A summer
daytime “warming hole (WH)” in the central U.S. was identified
observationally in the 20th century as well as in a regional model’s
future scenario climate in the mid-21st century.In
this talk we report the finding of additional major summer WHs (i.e.,
cooling centers) in
southeastern China and central South America that occurred in the 20th
century.All the three WHs are located
downstream of the world’s most predominant low-level jets (LLJ) areas
where mesoscale convective systems (MCSs) produce heavy summer rainfall
over
regions of intensive agriculture. Increased LLJ-related moisture
convergence in the WH regions enhanced cloudiness and thus resulted in
large attenuation of daytime solar radiation, partly explaining the
opposite trends in daily maximum and minimum temperatures in the WHs
during summer. The prominent MCS activity in WH regions increased
rainfall and moist in soil, thus reducing the daytime sensible heating
and resulting in cooling near the surface.