Abrupt climate change in the Arabian Peninsula mediated by the subtropical jet stream dynamics

The Arabian Peninsula (AP) has an arid climate with the whole annual precipitation falling in non-summer months, high levels of ambient dust, and extreme surface temperatures. The characteristics of the climate of the AP changed comprehensively since the late 1990s. The climate of the region is closely tied to the baroclinic activity mediated by the subtropical jet stream flowing over the northern region of the Peninsula. Synoptic disturbances on the Subtropical Jet over the Arabian Peninsula create and regulate most of the weather patterns in the region. The STJ has a high Ertel's potential vorticity gradient that acts as a restoring force for disturbances. Rossby waves formed by these disturbances create mid- and upper-level vortices downstream of the STJ exit, causing precipitation, deep convection, dust storms, and turbulent winds at the surface as they travel south. Changes in the STJ can cause significant variations in the frequency and strength of these disturbances, altering the region's climate. Here I show that there have been significant changes in the baroclinic activity after 1998: (a) the magnitude of the PV gradient in the region of the maximum PV gradient (MGPV) has decreased, and (b) the mean location of the latitude of the MGPV has generally moved north,. These changes resulted in lowered convection an increased stability of the region. CRU data shows that there have been abrupt changes in several climate variables in 1998: the mean and variance before and after 1998 are different. Thus, the distributions of climate variables changed before and after 1998. Abrupt changes in climate variables cannot be explained in a slowly changing climate. Here we decompose the mean meridional temperature gradient into its intrinsic constituent frequency components using Empirical Mode Decomposition, and show that: (a) the high frequency components gain strength after 1998, and (b) the low frequency components have a reduced magnitude after 1998. These time-frequency changes in terms of frequency and amplitude result in abrupt changes in almost all the climate variables.

These changes are likely to destabilize the sustainability of the region. Further, I will also discuss the implications of such an abrupt comprehensive climate change in the Arabian Peninsula, and keep the results in the context of global climate change.