HAPpy Hour- Some ideas about the improvement of bulk microphysical scheme: a novel parameterization for droplet formation and visibility reduction due to haze

Seminar - HAPpy Hour
Aug. 25, 2023

3:00 – 4:00 pm MDT

FL2-3107 or VIRTUAL
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Dr. Geresdi István

egyetemi tanár, doktori iskola vezető, Pécsi Tudományegyetem Természettudományi Kar

Bio-  I started my scientific career at the Hungarian Meteorological Service in 1980. I was involved in a hail suppression program. This was the time I made my first step on the field of numerical simulation of the microphysical processes. I got my PhD degree in 1992 in meteorology. I have had long term scientific cooperation with NCAR since 1998. I have made researches about development a bin microphysical scheme to study microphysical processes occur in different type of clouds, the impact of cloud seeding, and the interaction between cloud physics and cloud chemistry. Currently I am full professor at University of Pécs, Faculty of Sciences and the head of the Doctoral Committee of University of Pecs. I was the dean of the Faculty of Sciences between 2007 and 2013.

Abstract- A novel aerosol activation scheme was developed and implemented into the WRF Thompson Aerosol Aware microphysical module: 
(i) While in most of the NWP models the activation is based on the updraft even in the fog, in the novel parameterization the local rate of cooling and of the water vapor are considered in the evaluation of the aerosol activation rate.
(ii) Diagnostic variables are added to evaluate the visibility reduction due to formation of haze droplets. The impact of changing the activation scheme is demonstrated by a case study of a well observed fog event. 
The results are summarized as follows: 
(i) The inhomogeneous spatial and temporal distribution of the number concentration of droplets is an inherent characteristic of the novel parameterization scheme. 
(ii) Compared to the parameterization based on updraft, the novel parameterization scheme increases the number concentration of the droplets significantly, especially at the top of the fog. As a consequence, it reduces the downward shortwave radiation flux prolonging the lifetime of the fog by about 30-60 minutes. 
(iii) The novel method is able to evaluate the reduction of visibility due to haze.


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