Atmospheric Lapse Rate Regimes and Their Parameterization

Abstract

Lapse rates, moist adiabatic lapse rates and the critical lapse rate for baroclinic adjustment are calculated and compared for the mean annual, January and July states in the Northern Hemisphere. In the troposphere above the planetary boundary layer zonal mean lapse rates are within 20% of the moist adiabatic lapse rate from the equator up to about 30°N in January and 50°N in July, but are appreciably more stable in higher latitudes. The latitudinal distribution of tropospheric mean lapse rates clearly delineates two regimes in the atmosphere—a low-latitude regime where the lapse rates are essentially moist adiabatic, and a high-latitude regime where the lapse rates are essentially the critical lapse rate for baroclinic adjustment. The dividing point between the two regimes shifts from 28°N in January to 47°N in July, and the transition is less sharp in July than in January. The absence of appreciable seasonal changes in lapse rates in midlatitudes can be attributed to counterbalancing seasonal c... Abstract Lapse rates, moist adiabatic lapse rates and the critical lapse rate for baroclinic adjustment are calculated and compared for the mean annual, January and July states in the Northern Hemisphere. In the troposphere above the planetary boundary layer zonal mean lapse rates are within 20% of the moist adiabatic lapse rate from the equator up to about 30°N in January and 50°N in July, but are appreciably more stable in higher latitudes. The latitudinal distribution of tropospheric mean lapse rates clearly delineates two regimes in the atmosphere—a low-latitude regime where the lapse rates are essentially moist adiabatic, and a high-latitude regime where the lapse rates are essentially the critical lapse rate for baroclinic adjustment. The dividing point between the two regimes shifts from 28°N in January to 47°N in July, and the transition is less sharp in July than in January. The absence of appreciable seasonal changes in lapse rates in midlatitudes can be attributed to counterbalancing seasonal c...