Microphysics in Multi-scale Modeling System with Unified Physics

Ming Cai
Noon, Tuesday March 11, room 2155

We have developed indices measuring the total poleward mass transport into the upper troposphere and stratosphere above the Arctic and total equatorward air mass transport out of the lower polar troposphere on a daily basis using ERA-Interim reanalysis for the period of 1979-2011. These two indices are very highly positively correlated with little lead/lag, implying that a stronger poleward warm air mass circulation in the polar region tends to be compensated by a stronger equatorward mass transport by the cold air branch below and vice versa. We have also developed various indices that measure the continental-scale near surface warmness and coldness in high latitudes and mid-latitudes. It is shown that a lack of warm air mass flux into polar region is accompanied by weaker equatorward advancement of cold air near the surface. And, as a result, the cold air mass is largely imprisoned within polar circle, responsible for general warmness in mid-latitudes and below normal temperature in high latitudes. Conversely, a stronger warm air transport into polar upper atmosphere is accompanied by a stronger equatorward advancement of cold air near the surface, resulting in massive cold air outbreaks in mid-latitudes and anomalous warmth in high latitudes. We have also identified two dominant geographical patterns of cold air surge associated with strong mass circulation crossing 60N. One is massive cold air surges over both North America and Eurasian continents and the other is the dominance of cold air surges only over one of the two continents with the abnormal warmness over the other continent in the time periods of 1-10 days after a stronger mass circulation cross the polar circle. The first pattern explains the first and forth leading EOFs of winter season surface temperature anomalies whereas the second mode is related the second leading EOF modes.