Characteristics of the Mesoscale Precipitation Bands under the influence of Extratropical Cyclones in Heilongjiang Province during Cold Seasons

Abstract

Based on nine C-band Doppler radar observations of Heilongjiang Province and conventional data from 2010 to 2021， combined with 1-h interval ERA5 reanalysis data of 0.25°×0.25° from the European Center for Medium-Range Weather Forecasts， the types and activity characteristics of mesoscale precipitation bands associated with extratropical cyclones in Heilongjiang Province are statistically analyzed， and the similarities and differences in the environment fields of two types of mesoscale precipitation bands are compared through typical cases.The main results are： （1） Mesoscale precipitation bands are primarily divided into single， multi， transitory， and nonbanded.Precipitation bands are mainly located in southern and northeastern Heilongjiang and the northwest and northeast quadrants of surface cyclones， within 900 km from the cyclone centers， and occur in the mature stage of cyclones.The main movement types of mesoscale precipitation bands are laterally translating and hybrid.（2） Vertical profiles of physical quantities can well reflect differences in precipitation intensity of different precipitation bands.Single-banded bands have the most excellent low-level specific humidity and frontogenesis， causing the heaviest precipitation.Non-banded bands have extensively weaker low-level frontogenesis than single-banded bands， with maximum specific humidity near 800 hPa， causing a wide range of precipitation and a weaker precipitation intensity than single-banded bands.（3） The analysis of cases shows that both single-banded and multi-banded bands are located on the north side of the intense 850-hPa warm advection， the northeast quadrant of the surface cyclone， in a small moist symmetric stable or moist symmetric unstable environment.The direction of the mesoscale precipitation band is parallel to the frontogenesis.The differences between them are as follows： for the single-banded band， deformation leads to strong frontogenesis and the upward movement concentrated on a small area， accompanying the development and movement of the low-level low and the surface cyclone， while for the multi-banded， weak deformation and shallow frontogenesis accompanying little movement and intensity change， intense upper-level divergence and low-level warm advection caused more extensive upward motion with multiple upward centers， corresponding to multi bands.

Keywords

• extratropical cyclone
• mesoscale precipitation band
• frontogenesis
• moist symmetry instability