Assessing Desert Dust Indirect Effects on Cloud Microphysics through a Cloud Nucleation Scheme: A Case Study over the Western Mediterranean

Konstantinos Tsarpalis,Nikolaos Mihalopoulos,Anastasios Papadopoulos,Petros Katsafados

doi:10.3390/rs12213473

Abstract

In this study, the performance and characteristics of the advanced cloud nucleation scheme of Fountoukis and Nenes, embedded in the fully coupled Weather Research and Forecasting/Chemistry (WRF/Chem) model, are investigated. Furthermore, the impact of dust particles on the distribution of the cloud condensation nuclei (CCN) and the way they modify the pattern of the precipitation are also examined. For the simulation of dust particle concentration, the Georgia Tech Goddard Global Ozone Chemistry Aerosol Radiation and Transport of Air Force Weather Agency (GOCART-AFWA) is used as it includes components for the representation of dust emission and transport. The aerosol activation parameterization scheme of Fountoukis and Nenes has been implemented in the six-class WRF double-moment (WDM6) microphysics scheme, which treats the CCN distribution as a prognostic variable, but does not take into account the concentration of dust aerosols. Additionally, the presence of dust particles that may facilitate the activation of CCN into cloud or rain droplets has also been incorporated in the cumulus scheme of Grell and Freitas. The embedded scheme is assessed through a case study of significant dust advection over the Western Mediterranean, characterized by severe rainfall. Inclusion of CCN based on prognostic dust particles leads to the suppression of precipitation over hazy areas. On the contrary, precipitation is enhanced over areas away from the dust event. The new prognostic CCN distribution improves in general the forecasting skill of the model as bias scores, the root mean square error (RMSE), false alarm ratio (FAR) and frequencies of missed forecasts (FOM) are limited when modelled data are compared against satellite, LIDAR and aircraft observations.

Highlights

Dust particles cover approximately 50% of the global load of the natural airborne particles [1,2]
A spatial pressure fieRldadisiaftoiormn escdhwemhiech is directly linked to the gReRneTrMatGion[9o3]f significant pre and post frontal winds resSpuornfsaicbelelafyoerrthscehdeumset triggering anMdotnrainn–spOobrutk[9o7v].STimheilaevrietyntTohfe2o0r–y2[59J4u]ne 2013 has been chosen, as iLtawndassuarsfsaocceiastcehdemweith torrential rainNfaollashoLvaenrdWsuesrftaercne mEuordoepl e[9c5a]used by a lowpressure systemBpoeurnsdisateryncleayoevresrcthheemIbeerian Peninsula
The potential indirect effects of desert dust aerosols on cloud formation and precipitation have been investigated in this study through the implementation of the revised Fountoukis and Nenes [55] cloud nucleation scheme (FN scheme) in the fully coupled meteorology–chemistry model WRF/Chem

Summary

Introduction

Dust particles cover approximately 50% of the global load of the natural airborne particles [1,2]. Dust aerosols interact with electromagnetic radiation [3] and directly affect the radiation budget of the land–atmosphere system (aerosol direct effect) [4]. They absorb and scatter in various wave lengths both solar and long wave radiation [5,6,7,8]. They modify the heating rates, the stability and the stratification of the atmosphere [9,10]. Dust particles have an important impact on human health [14,15,16,17,18] and alter the biochemical cycles of both land and sea ecosystems [19]

Methods

Results

Conclusion