Cloud Resolving Studies of Trace Gas Scavenging and Photochemistry

A cloud resolving online chemistry transport model was developed based on WRF and has been used to study the transport of trace gases, the scavenging of soluble trace gases, and influences of lightning produced nitrogen oxides (NOx=NO+NO2) on local photochemistry. This presentation mainly focuses on the influence of the retention coefficient (i.e. the fraction of a dissolved trace gas which is retained in hydrometeors during freezing) on the vertical re-distribution of soluble trace gases by deep convective clouds. A few previous model studies (Crutzen and Lawrence 2000; Mari et al. 2000; Barth et al. 2001; Yin et al. 2002) have suggested that even highly soluble trace gases can reach the upper troposphere if they are ejected from freezing hydrometeors at high altitudes. Here, results from cloud system resolving model runs (in which deep convection is initiated by small random perturbations and so-called ”large scale forcings” are prescribed) for a tropical oceanic (TOGACOARE) and a mid-latitude continental case (ARM) are compared to runs in which a bubble was used to initiate deep convection (STERAO, ARM). Furthermore, the modeled ozone budget in the TOGA-COARE/CEPEX region (located in the tropical West Pacific) including influences of lightning NOx is briefly discussed.