Abstract:

There are significant climate differences between the north and south of Ningxia; however, the evolution characteristics and factors influencing precipitation spatial patterns closely related to ecology require more detailed and in-depth analysis. Using climate statistical diagnostic methods, this research examines precipitation data during the flood season for 20 meteorological stations in Ningxia, NCEP/NCAR atmospheric reanalysis, sea surface temperature and Arctic sea ice data from 1961 to 2022. An abnormal index for the north-south pattern of precipitation during the flood season in Ningxia was identified and explored the possible impact of the synergy of Pacific sea surface temperature and Arctic sea ice signals driving this anomaly. The results show that the characteristic components of the north-south reverse phase of precipitation during the flood season in Ningxia have significant interdecadal variations. The frequency of the typical “northern flood and southern drought” distribution patterns increased significantly in the recent interdecadal background compared with before 1991, the proportion of the north-south reverse phase distribution pattern increased, and the north-south difference become more obvious. The synergistic (consistent phase) and antagonistic (opposite phase) effects of key indicators of Pacific sea surface temperature (I_sst) and Arctic sea ice (I_ice) cause abnormal geopotential heights over the Ural Mountains, Lake Baikal, and the Okhotsk Sea, resulting in different impact paths of cold air and positions of water vapor transport. When I_sst and I_ice are both positive, Ningxia is prone to the distribution pattern of “southern flooding and northern drought” during the flood season, characterized mainly by more precipitation in the southern region, less in the northern region, and more in the southern region than in the northern region. When I_sst is positive and I_ice is negative, the “northern flooding and southern drought” distribution pattern is likely to occur, especially when the northern region has more precipitation and the southern region has less. When I_sst and I_ice are both negative, the “northern flooding and southern drought” distribution pattern was likely to occur, mainly because of more precipitation in the northern region, less precipitation in the southern region, and less precipitation in the northern region compared with the southern region. When I_sst is negative and I_ice is positive, this was mainly due to the precipitation in the southern and northern regions being lower.

Key words: precipitation distribution, sea surface temperature, sea ice, synergy effect, Ningxia