The attribution study of extreme weather events has attracted the interests of climate change science communities in recent years. From July–August 2022, an extraordinary heatwave with record-breaking high temperatures occurred in Central and Eastern China, especially over the Yangtze River Basin, for what period the China Meteorological Administration gave the first “red heat warning” in history. Meanwhile, the western Pacific subtropical high leaped over the Tibetan Plateau, which was rarely seen in the past. Understanding the causes of such extreme events and distinguishing the role of human played are both helpful for mitigation and adaptation of climate change, although it is full of challenges. This study used a risk ratio approach (PR) to investigate whether and to what extent atmospheric circulation and other factors (such as anthropogenic climate change, greenhouse gases, and aerosols) contributed to this event, 42 members out of 12 CMIP6 models. According to the CMIP6 simulations, the contribution results show that the existence of anomalous anticyclones would have increased the probability of this extreme heatwave by 4.5 times, making it the main driver for this extreme event in the past 60 years, while the anthropogenic climate change contributed the most (PR = 3.9) for the past 30 years. Additionally, we found that anthropogenic aerosols had no significant impact on the likelihood of this event (PR = 0.82 (0.74) in the past 30 (60) years). This study provides a strong warning that global warming caused by anthropogenic activities in recent decades may result in more frequent extreme heatwaves of summers similar to the summer of 2022. Therefore, measures for mitigating and adapting to global warming are urgently needed.

How to cite: Liang, W. and Dong, W.: How did anthropogenic forcing influence the exceptional heatwave in the summer of 2022 over the Yangtze River Basin through subtropical high?, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2695, https://doi.org/10.5194/egusphere-egu23-2695, 2023.

The Tibetan Plateau (TP), known as the ‘Third Pole’ region, is one of the most sensitive places to global climate change, which possesses the highest surface incident solar radiation (SSR) in China. In the 2021 growing season, i.e., May to September, southeastern Tibetan Plateau (SETP) registered a widespread and extremely low SSR since 1950 with approximately -18.65 W/m² of regional mean anomaly relative to 1950-1979 mean. Through the analyses using observations, reanalysis and CMIP6 model simulations, the extremely low SSR event in 2021 is mainly attributed to more clouds and abundant atmospheric moisture caused by anomalous southerlies from the Bay of Bengal. The existence of abnormal south winds could increase the probability ratio of such low SSR events like 2021 to be 9.25 (95% CI: 6.56-19.02). Anthropogenic aerosols and GHGs-induced warming might increase the probability of such SSR events to be a factor of 4.70 (95% CI: 1.66-15.49) and 1.66 (95% CI: 1.01-6.59), respectively. As a result, the extremely low SSR event could significantly reduce local gross primary productivity in the 2021 growing season over SETP, especially in the humid eastern SETP where SSR has a stronger impact on vegetation photosynthesis.

How to cite: He, Y., Yang, K., Ren, Y., Zou, M., Yuan, X., and Tang, W.: Causes of the extremely low solar radiation in the 2021 growing season over southeastern Tibetan Plateau and its impact on vegetation growth, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-918, https://doi.org/10.5194/egusphere-egu23-918, 2023.

In late September 2022, the Atlantic Hurricane Fiona transitioned to an extratropical cyclone making a landfall in the Canadian Atlantic provinces and setting a new national lowest pressure record. The insured damage from the resulting windstorm and flooding is estimated to be 800 million CAD (600 million USD).

In this study, we analyze the maximum daily near-surface wind speeds in Atlantic Canada using reanalysis and CMIP6 HighResMIP data. According to our preliminary results from ERA5 reanalysis, the 2022 Fiona wind speeds were the highest in Atlantic Canada since 1950, with an estimated return period of 500 years. Additionally, using HighResMIP data from the models with a spatial resolution exceeding 56x56 km, we compare the wind speeds in the current climate with those from 1950-1969 and in 2031-2050 under the highres-future scenario, similar to RCP8.5. While currently in Atlantic Canada, there is no statistically significant increase in the maximum daily wind speeds in comparison to 1950-1969 climate, the increase in the mid-21^st century wind speeds in comparison to the 1950-1969 period is statistically significant with the 2022 event being 3.8 times more likely. We apply similar analysis to the data from CAM5 model as well as to the CMIP6 precipitation data in the region.

How to cite: Malinina, E. and Gillett, N.: Attribution of the 2022 extratropical storm Fiona, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10176, https://doi.org/10.5194/egusphere-egu23-10176, 2023.

Nowadays, the intensification of global warming leads to the increased frequency of extreme temperature events. Many studies reported that different regions are facing the threat of extreme hot and cold temperature in some degree. The Qinghai-Tibet Plateau Transportation Project is a major project in China, and it is beneficial for public to study the extreme temperature events along the railway and avoid the risk induced by the extreme temperature. This study estimated the daily maximum, minimum and average near-surface air temperature along the railway. Sixteen extreme temperature indices defined by ETCCDI (the Expert Team on Climate Change Detection and Indicators) were used to represent the extreme temperature events, and Mann-Kendall trend test and Sen's slope estimation method were employed to explore the spatial-temporal variation trends of the extreme temperature along the Qinghai-Tibet Plateau Transportation Corridor from 1981 to 2019. In addition, the response of extreme temperature events to altitude was discussed.

The results show that the climate becomes warming along the Qinghai-Tibet Plateau Transportation Corridor from 1981 to 2019, and the extreme hot events are detected in most areas, while the extreme cold events mainly occurs in the east and southwest part. The significant increasing trend is found according to the indices representing the hot events (SU25, TR20, TX90p, TN90p, TXx, TXn, TNx, TNn and WSDI), while the indices representing the cold events (FD0, ID15, TX10p, TN10p and CSDI) show a significant decreasing trend in most areas over the past nearly 40 years. Besides, the extreme temperature events is highly related to altitude variations. Compared with the middle altitude zones, extreme high temperature events tend to occur in the lower altitude zones and the higher altitude zones. It is of great significant to schedule the train in advance and reduce the disasters by investigating the long-term variation trends of extreme temperature events along the Qinghai-Tibet Plateau Transportation Corridor.

How to cite: Wang, B., Gao, M., and Li, Z.: Analysis of extreme temperature events based on estimated 1-km daily near-surface air temperature, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8417, https://doi.org/10.5194/egusphere-egu23-8417, 2023.

During the XX and the beginning of the XXI century, significant warming caused by the emission of greenhouse gases, mainly CO₂ and CH₄ into the atmosphere, is observed. The fifth assessment report of the Intergovernmental Panel on Climate Change estimated a warming of 0.85˚C ± 0.20˚C during 1880-2012. This global warming has been changing atmospheric circulation patterns, which can result in accelerating and intensifying extreme weather events such as more violent storms, floods, droughts, heat and cold waves. The weather extremes can cause economic loss, as well as loss of human lives.

In this study, the variations in 25 extreme temperature and precipitation indices defined by ETCCDI, are examined using probability distribution analysis and spatial statistics for periods of 71 to 137 years for 16 stations such as Ai-Petri, Askaniia-Nova, Chernivtsi, Feodosiya, Kerch, Kyiv, Lubny, Luhansk, Lviv, Mykolaiv, Odesa, Poltava, Shepetivka, Uzhhorod, Uman, Vinnytsia. The indices data were obtained from www.ecad.eu.

For Ukraine average, in the last 30 years, the number of summer days, warm days and nights, and warm spell duration index have reached historical highest values, while the number of cold days and nights, frost and icing days, and cold spell duration index reached the recorded lowest values.

The distribution characteristics of extreme temperature indices showed the increased frequency of warm events is higher in the west of Ukraine than in its others regions while, on the contrary, the decreased frequency of cold events is higher in the rest of the country than in its western part.

For all territory of Ukraine, an increase in maximum daily and maximum 5 days precipitation amount, the maximum number of consecutive wet days, heavy and very heavy precipitation days, and a decrease in the maximum number of consecutive dry days are observed for the last three decades.

A combination of harmonic regression and spectral analysis was applied to the time series for which the Mann-Kendal method revealed statistically significant trends, to predict the annual and seasonal temperature and precipitation, maxima of daily maximum temperature, minima of daily minimum temperature, maximum 1-day precipitation amount and consecutive dry days up to 2050.

The annual temperature was predicted to increase in the study area, with an increasing rate of 0.3-0.5°C decade⁻¹ up to 2050. The increasing rate of the maxima value of the daily maximum temperature is the same. Minima value of daily minimum temperature was predicted to increase the most from 0.44 to 0.62°C decade⁻¹. Seasonal values of all indices were predicted to grow, especially in summer and winter for maxima of daily maximum temperature and in spring for minima of daily minimum temperature.

Precipitation is predicted to increase in the range of 4 to 22 mm in decade⁻¹, the most increasing rate will be observed in stations located in the western and central parts of Ukraine. For the period up to 2050 for most of the territory of Ukraine time series of annual and seasonal maximum 1-day precipitation showed slightly increasing trends while the annual and seasonal consecutive dry days are anticipated to decrease insignificantly.

How to cite: Bohushenko, A., Khomenko, I., and Stepanenko,, S.: Climate variability, trends and extreme events in Ukraine, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12175, https://doi.org/10.5194/egusphere-egu23-12175, 2023.

    Soil moisture is the primary indicator for assessing agricultural and ecological drought, and its relationship with temperature has a great impact on regional climates, such as triggering heat waves. So far, studies on the coupling relationship between soil moisture and temperature have mainly focused on arid or semi-arid regions with strong land-atmosphere coupling. However, less attention has been paid to humid regions with relatively weak coupling between soil moisture and temperature there. In recent years, a number of studies have found that heat waves in humid regions are directly related to the coupling of soil moisture and temperature. Nevertheless, historical changes of soil moisture and its relationship with temperature in humid areas are still unclear.
    In this study, three sampling sites with published long-term tree ring δ¹⁸O records in England and France were selected to reconstruct the surface (0–10 cm) soil moisture changes in Western Europe (40°N–55°N, 10°W–10°E) from 1360 to 2000 AD. Various abrupt-change detecting tests (Mann-Kendall test, Yamamoto method, and Bernaola-Galvan segmentation algorithm) showed that soil moisture began to decline suddenly around 1820, with increasing dry years and decreasing wet years, and no wet years after 1950 . After 1820, the coupling of soil moisture and temperature was growing stronger than before. Compared with the historical period, the summer sea level pressure anomaly is stronger in the dry years after 1820, which may be related to the weakened westerly circulation and water vapor transport. These findings suggest that, in the context of global warming, hotter and drier conditions are occurring not only in arid regions, but also in humid western Europe. Under future warming scenarios, humid regions may also be threatened by hot droughts.

How to cite: Wang, L., Liu, H., Chen, D., Zhang, P., Leavitt, S., Liu, Y., Fang, C., Sun, C., Cai, Q., Gui, Z., Liang, B., Shi, L., Liu, F., Zheng, Y., and Grießinger, J.: The 1820s Marks a Shift to Hotter‐Drier Summers in Western Europe Since 1360, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2176, https://doi.org/10.5194/egusphere-egu23-2176, 2023.

The Republic of Djibouti is a small country (23 200 km²) in East Africa, characterised by an arid context coupled with a high variability of rainfall that generates flash floods causing severe damage to the population and infrastructure. The mechanisms controlling climate dynamics in Djibouti and the Eastern Africa region remain poorly understood. In this study, we document the atmospheric mechanisms associated with extreme rainfall events in the Republic of Djibouti. To that end, we use at the daily timescale rain-gauge data (a network of 36 stations on the period 2013-2020), satellite-based rainfall estimates (CHIRPS, IMERG, MSWEP and RFE) and atmospheric reanalyses (ERA5), selected over their common period 2001-2020.

A multivariate Hierarchical Ascendant Classification of rainy days in Djibouti (≥ 10% of grid-points exceeding 1 mm.day-1, according to all four satellite products) reveal 4 clusters (intense rainfall, moderate rainfall, rainy in the southwest, rainy in the east) which differentiate from each other by the intensity and spatial extent of rainfall. These clusters show a non-homogeneous seasonal distribution, occurring mainly in the March-April-May (MAM) and July-August-September (JAS) seasons, and more rarely in October-November-December (OND). The atmospheric circulation anomaly patterns associated with the clusters are quite similar and highly season-dependent. In MAM most clusters display an anomalous trough over the Red Sea from 700 hPa to 200 hPa. In JAS, an anomalous low over the southern Red Sea drives a thicker than normal monsoon flow at 700 hPa (especially for the southwest cluster), while upper northerlies prevail at 200 hPa. In OND, most rainy events result from moisture advection from the Western Indian Ocean favoured by positive phases of the Indian Ocean Dipole. Some highly unusual atmospheric circulation patterns, which are not depicted by the above classification (e.g., associated with tropical cyclones), also result in intense rainfall events in the Republic of Djibouti.

How to cite: Mohamed Waberi, M., Camberlin, P., Pohl, B., and Assowe, O.: Atmospheric Drivers of Rainfall Events in the Republic of Djibouti, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4223, https://doi.org/10.5194/egusphere-egu23-4223, 2023.

Extreme precipitation events have enormous impacts on the natural and human aspects of most regions. This study presents a detection and attribution analysis of extreme precipitation in the Asian monsoon region (AM) from 1950 to 2014 using the Coupled Model Intercomparison Project Phase 6 (CMIP6) models. The observed positive PI (probability-based index) trends for annual maxima of 5-day (Rx5day) and 1-day (Rx1day) precipitation accumulations are 6.04%/100yr and 10.96%/100yr. The simulated PI trends for Rx5day and Rx1day under greenhouse-gas (GHG) forcing are 9.70% /100yr and 10.86% /100yr, respectively, while the trends are −8.99% /100yr and −7.01%/100yr under the aerosol (AER) forcing. Greenhouse-gas concentrations alone cause extreme precipitation increases, while the offsetting effects of anthropogenic aerosols may result in weaker increasing trends in ALL forcing simulations. The anthropogenic (ANT) signals are detectable, while the natural (NAT) signals could not be distinguished from the noise (internal climate variability) based on the optimal fingerprinting method. GHG forcing is detected for AM’s extreme precipitation when GHG, AER, and NAT forcing are all considered. A three-signal analysis confirms that CO₂ forcing had a detectable influence on observations, whereas the influence of volcanic and solar-irradiance forcings could not be distinguished. Our results provide evidence that anthropogenic greenhouse gases (mainly CO₂) are the prime external factors influencing the increase of AM’s extreme precipitation.

How to cite: Dong, T., Dong, W., and Zhu, X.: Detection and attribution of extreme precipitation events over the Asian monsoon region, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4762, https://doi.org/10.5194/egusphere-egu23-4762, 2023.

Summer monsoon precipitation provides crucial water resources for agriculture, industry, and life in East Asia (EA). Meanwhile, it causes disasters when occurring over highly populated regions. Recently, we have witnessed a series of extreme precipitation events in South Korea, China, and Japan during the summer monsoon season. It remains uncertain whether these events and the EA summer monsoon precipitation system are affected by the ongoing climate changes. The summer precipitation in EA is contributed by various extra-tropical cyclones, fronts, and other weather systems. Here, we focus on the stationary front-induced precipitation, which accounts for more than 30% of EA summer precipitation. Based on objectively detected frontal systems, we found that the intensity of observed frontal rainfall increased by 19.8% during 1991–2015. It was further shown that the intensity increase of frontal rainfall is mainly attributed to anthropogenic greenhouse gas forcing on the basis of the Community Earth System Model Large Ensemble simulations. We found that the reinforced western North Pacific subtropical high makes enhanced water vapor convergence in the lower troposphere along its rim. This study confirms that the frontal summer monsoon precipitation system over EA has been intensified significantly by human-induced global warming, which will likely enhance further in the future.

How to cite: Moon, S., Utsumi, N., Jeong, J.-H., Yoon, J.-H., Wang, S.-Y. S., Shiogama, H., and Kim, H.: Anthropogenic Intensification of East Asia Summer Monsoon Frontal Precipitation System, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10686, https://doi.org/10.5194/egusphere-egu23-10686, 2023.

Attention of tropical cyclone (TC) induced remote moisture transport has increased over the past several decades. There is significant progress of objective identification to resolve spatiotemporal merging and spitting of the moisture transport patterns using digraphs to represent clusters inside the patterns. This identification method also reflects discontinuous and uneven moisture transport. However, finding the mainstreams of these patterns still remains a challenge, which is necessary to retrieve statistical and geometric features of these patterns. To solve this issue, we assign the weight that is positive and decreases with increasing cross-border moisture transport between two clusters corresponding to two nodes to their edges to process the strongest connected component and dijkstra shortest path algorithms to find the main stream of moisture transport pathways. The frequency of TC remote transport is the highest in July over North China and Korean Peninsula and in September over South China and northern Vietnam. The statistical and geometric features of TC remote moisture transport are analyzed in the key periods and regions above. Moreover, discontinuity of moisture transport over the key periods and regions is quantified by the temporal variability of weights over the lifecycles of moisture transport patterns. Unevenness of moisture transport is quantified by the spatial variability of length of the mainstream. Vertical cross section of physical decomposition of moisture transport along the mainstream is further analyzed in this study.

How to cite: Xiao, S., Zhang, A., Chen, Y., and Li, W.: Spatiotemporal Characteristics of Tropical Cyclone Induced Remote Moisture Transport affecting East Asia using Digraphs, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17091, https://doi.org/10.5194/egusphere-egu23-17091, 2023.

Understanding extreme precipitation is essential for mitigating the associated risk. This study analysed eight Coupled Model Inter-comparison Project phase 6 (CMIP6) models by capturing daily, seasonal, yearly, and extreme precipitation over Bangladesh during the period 1961-2014, treating ECMWF Reanalysis v5 (ERA5) rainfall reanalysis data as an observational reference. Sixteen extreme precipitation definitions were found in the literature, implemented, and used in a comparative analysis in Bangladesh, one of the most vulnerable countries to climate change. Definitions used in the literature, duration definitions, such as the Consecutive Dry Days (CDD) and the Consecutive Wet Days (CWD), frequency definitions, such as the days when precipitation is at least 10 mm, 20 mm, 30 mm, at least 65 mm but less than 100 mm, at least 100 mm but less than 115 mm, at least 115 mm but less than 205 mm, and at least 205 mm, and intensity definitions, such as SDII, RX1day, RX3day, RX5day, PRCPTOT, R95pTOT, and R99pTOT. Temporal trends in extreme events identified by 16 different methods were assessed using both the modified Mann-Kendall (MK) method and Sen's Slope Estimator (SSE).

Analysis of the ERA5 reanalysis product indicated a 0.33-day-per-year increase in consecutive dry days (CDD) during 1961-2014 over Bangladesh, revealing that Bangladesh may be drying out at a faster rate than previously anticipated. For average daily wet-day precipitation intensity (SDII), ERA5 and MIROC6 showed a decrease at annual rates of -0.07 and -0.06 mm per day, respectively. If these trends continue over the next few years, Bangladesh may encounter water scarcity. In addition, a decrease at a rate of -0.09 days per year in R65mm was found in ERA5, while other frequency definitions do not have statistically significant trends. MIROC-ES2L has the closest agreement to ERA5 in terms of Percentage BIAS (PBIAS), R-Squared (R2), Root Mean Squared Error (RMSE), and Mean Squared Error (MSE) metrics, followed by EC-Earth3-Veg-LR, IPSL-CM6A-LR, and MIROC6. Several recommendations for future studies and improvements are also included in this study. Results presented in this study, specifically a faster drying rate, fewer days with 65-100 mm of daily precipitation, and possibly less monsoon seasonal precipitation are important for the development of adaptation strategies in Bangladesh.

How to cite: Huang, Y.: Analysis of extreme precipitation in Bangladesh based on reanalysis data and climate models, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2403, https://doi.org/10.5194/egusphere-egu23-2403, 2023.

Rainfall estimation in ungauged areas is becoming one of the research hotspots recently. From a case study in the UK, this study builds a sub-daily rainfall estimation model based on more widely available daily series data from 151 gauges. In this study, we stratify the scaling properties of UK rainfall into homogenous rainfall zones, geophysical factors, seasons, and air masses to investigate how these scaling properties change temporally and spatially. We use temporal scaling techniques to extract the scaling relationship between sub-daily rainfall intensity and annual maximum series along with all possible factors introduced above. The estimated rainfall is validated with observed rainfall data and shows a higher degree of agreement. Finally, we compare the IDF (Intensity-Duration-Frequency) curves for both estimated and observed data. Such scaling relationships can support scientists and governments to estimate extreme rainfall at a specific duration and return period in ungauged regions. This method can also generate design rainfall time series for flood simulation models to evaluate present and future pluvial flood risks in urban areas.

How to cite: Wang, Z., Wilby, R., and Yu, D.: Temporal scaling properties of extreme rainfall and intensity-duration-frequency curves in the UK, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4473, https://doi.org/10.5194/egusphere-egu23-4473, 2023.

As still-water bodies, the change of lakes reflects the effect of climate change and human activities and play as sentinels of the earth. It has been witnessed that the detailed area change of lakes on Tibetan Plateau (TP) are more sensitive to global warming than the many other places of the world. Among them, small lakes are especially abundant in number, having disproportionately high hydrology and nutrient processing rates, and playing an irreplaceable role in regional and global carbon and nitrogen cycle meanwhile. It has been proved that the change small lakes and ponds, like emerging and disappearing, show strong correlation with that of precipitation, permafrost, and ecological systems in Arctic. However, as the third pole on earth with extremely complex terrain and physical surface properties, the small lakes are also a unique part while has not been investigated thoroughly. Based on the cloud computing platform Google Earth Engine (GEE), this study focused on the 11,400 small lakes on TP (lakes with max area between 0.1 and 1 km²) to answer the question that how the emergence and vanishing of small lakes responses to the climate change from 1972 to 2019. The lakes with area shrinking below 0.01 km are regarded as vanished, while area increasing above the value are regarded as emerged. Comparing with Ocean Nino Index (ONI) and and in-situ precipitation data, preliminary results show that: 1. the severe El-Nino events have been well captured by the emergence and vanishing of small lakes; 2. the emergence and vanishing of small lakes have a negative relationship in each year and the emergence peaks have about one-year time lag after those vanishing peaks; 3. the net emergence rate of small lakes has strong positive relationship with precipitation. This work could support further studies on the relationship among climate change, carbon cycle, and water cycles on Tibetan Plateau.

How to cite: Li, H.: Small lakes on Tibetan Plateau act as a climate change indicator, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4496, https://doi.org/10.5194/egusphere-egu23-4496, 2023.

Wetland is one of the ecosystem types with the largest density of organic carbon pool. The threat of declining wetland water level to carbon pools and the resulting greenhouse gas (GHG) emissions have attracted much attention. However, an assessment of emissions from degraded wetlands containing the three major greenhouse gases is still lacking. We compiled a global GHG exchange dataset that shows the non-linear water-heat pattern of GHG emissions. Combined with the Wetland Extended Trends Index, we estimated that the total GHG emissions from global degraded wetlands are 276.4 Gt CO₂eq during 1950-2020. The emissions of carbon dioxide, methane, and nitrous oxide are equivalent to 10.8%, - 0.5%, and 30.5% of anthropogenic sources, respectively. Under the historical trend of wetland degradation, the emissions may increase by 1.5 times from 2021 to 2100, reaching 408 Gt CO₂eq. Accordingly, wetland restoration can reduce anthropogenic carbon dioxide emissions by 10%.

How to cite: Zou, J. and Zeng, Z.: Assessment of greenhouse gas emissions and mitigation potential in global degraded wetlands, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10440, https://doi.org/10.5194/egusphere-egu23-10440, 2023.

El Niño–Southern Oscillation is the most important source of interannual variability in the tropics; it also exerts great influences on weather and climate systems in local and remote regions through teleconnections. Observed influences of canonical (or eastern Pacific) El Niño on springtime extreme rainfall in East Asia (EA) are studied, and compared with the Coupled Model Intercomparison Project phase 6 (CMIP6) historical runs. Both model and observational data indicate that the anomalous low-level western north Pacific (WNP) anticyclone is the primary contributor to EA springtime extremes during El Niño. On a day-to-day basis, intense daily precipitation is related to enhanced upper-level synoptic-scale waves. Here we use a temperature advection index (TAI) to represent the amount of synoptic-scale activities. It was found that, when EP El Nino occurs, 85% of Yangtze River Basin (YRB)-South Korea (SK)-south of Japan (SP) extreme events are accompanied by instances of positive TAI (as compared to 72% in the climatological sense). However, such a change of association with TAI is not found in CMIP6. Observations further show a stationary wave pattern trapped along the intensified EA westerly jet during EP El Niño, which favors the development of synoptic-scale activity. There is also enhanced moisture transported from WNP to SK-SP, leading to more extreme precipitation in the region. In contrast, the interannual-scale westerly waveguide effect during EP El Niño is poorly simulated in CMIP6 models, resulting in models’ failure in capturing the contemporaneous YRB-SK-SP extreme precipitation changes.

How to cite: Cao, D., Tam, C.-Y., and Xu, K.: Simulating Springtime Extreme Rainfall in East Asia during Eastern-Pacific El Niño - Importance of Synoptic-Scale Activities and the Westerly Waveguide, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7202, https://doi.org/10.5194/egusphere-egu23-7202, 2023.

This study proposes dynamical downscaling simulations-high resolution of 12 km- by Weather Research and Forecasting (WRF) model, over the Arabian Peninsula. The downscaling of the Community Climate System Model (CCSM), to simulate (2000–2010), and future (2050–2060) time periods. The Arabian Peninsula is experiencing extreme weather events characterized by large precipitation and above average summer maximum temperatures, which are strong indicators of the climate change impact in the region.  The CCSM-WRF model values were evaluated against values obtained by the Center for Climate Integrity (CCI) on a monthly basis, and during extreme weather events 10 years’ period (2000-2010). The CCSM-WRF results at 12 km are comparable with published outcomes of high-resolution regional climate models, and shows better performance especially during the extreme events over the region (flash floods and heat waves). The future projection of the model shows that the maximum summer average values of temperature, soil temperature, and soil moisture, will increase in the next 30 to 40 years.

How to cite: Alsarraf, H. and Kokkalis, P.: WRF Dynamical Downscaling of CCSM over the Arabian Peninsula, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9547, https://doi.org/10.5194/egusphere-egu23-9547, 2023.

Changes in extreme precipitation in East Asia during the spring and Mei-yu seasons under global warming are evaluated based on two sets of high-resolution simulations with various warming pattern of sea surface temperature changes (SST' _spa). In the spring season, extreme precipitation exhibits larger enhancements over the northern flank of the prevailing rainy region in conjunction with a shifting tendency of more frequent extreme precipitation events and northward enhancement in the probability distribution, indicating a northward extension of future spring rainband. Enhanced precipitation intensity in conjunction with less rainfall occurrence and prolonged consecutive dry days lead to a minor change in mean precipitation, implying a more difficult water resource management in the warmer climate. The projected enhancement in precipitation intensity is robust compared with the internal variability related to initial conditions and the uncertainty caused by SST'_spa. In the Mei-yu season, extreme precipitation is intensified with a distribution of more frequent and more intense extreme events over the prevailing rainband region. The thermodynamic component of moisture flux predominantly contributes to changes in the spring season while both the thermodynamic and dynamic components of moisture flux contribute to the enhanced moisture transport furnishing the intensification of Mei-yu extreme precipitation from southern China to northeast Asia. Projecting future Mei-yu precipitation change is more difficult because of its higher uncertainty associated with 1) the larger variability embedded in the projection of extreme precipitation and 2) the model mean state that determines the spatial distribution of precipitation enhancement. 

How to cite: Chen, C., Hsu, H.-H., Liang, H.-C., Chiu, P.-G., and Tu, C.-Y.: Projection of Extreme Precipitation in East Asian Spring and Mei-yu Seasons in the Warmer Climate, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16796, https://doi.org/10.5194/egusphere-egu23-16796, 2023.

Anomalous episodes of extremely high surface temperature are heat waves, observational studies have shown that heat wave characteristics like intensity, frequency, and duration are increasing regionally and globally. As heat waves inflict disastrous impacts on the livelihood of millions of people, it is critical in developing suitable mitigation strategies to curtail the socio-economic vulnerability. Future projections at the regional level will be crucial for climate risk management to policymakers. The present study addresses the changes in the heat wave characteristics over the seven temperature homogeneous zones of India, viz. North West, North Central, West Coast, East Coast, Interior Peninsula, Western Himalaya, and North East. We use the historical (1951-2014) and projections (2015-2100) of the Coupled Model Intercomparison Project phase-6 (CMIP6) under different climate change scenarios based on Shared Socioeconomic pathways, SSP126, SSP245, SSP370, and SSP585. The reliability assessment has been carried out and the selected model composite showed good skill than all model composite, in the multiple aspects of observed heat wave features over each zone. The findings show that the projected area of occurrence of extreme daily maximum temperature and long-lasting heat waves (>11 days) are considerably increasing over all zones, where the exacerbating increase is over West Coast under all climate change scenarios.  The heat wave days are likely to increase two times over Western Himalaya and North West,  while the warm days are increasing four-fold over West Coast and double over other zones under SSP370 and SSP585.  The projected changes in heat wave characteristics over North East is below the all-India average. High-intensity heat waves are probably over the coastal zones under the scenario SSP370 and SSP585. Currently, the least heat wave impacted West Coast,  likely to be more vulnerable in the future. The projections show the heat wave characteristics are increasing over all the zones and have a spatio-temporal variation.

How to cite: Chathu, N. and Ramesh, K. V.: Future Projections of Heat Waves over India under CMIP6 Scenarios, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-268, https://doi.org/10.5194/egusphere-egu23-268, 2023.