The Aerosol Radiative Effect on Precipitation and Circulation associated with the Madden-Julian Oscillation over the Maritime Continent
Abstract
The aerosol radiative effect on precipitation and circulation associated with the Madden-Julian oscillation over the Maritime Continent (MC) is investigated using cloud-permitting regional model (WRF) simulations. The experiments are performed for the period from December 1 to 4, 2011, during which the MJO-envelope is located over the MC. A series of sensitivity experiments are performed by changing the background aerosol number concentration (cm-3) in the planetary boundary layer (PBL), with decreasing exponentially with height above the PBL. In the CONTROL experiment (aerosol number concentration of 1500 is set), the distribution of precipitation over the sea and land is comparable to observation, which precipitation over sea is higher (15%~20%) than that over the land when the MJO-envelope propagates across the MC successfully. As the aerosol number concentration increases, precipitation over the sea is significantly stronger than over land due to aerosol as a radiation absorber. In other words, as higher concentrated aerosol (high condition) absorbs more solar radiation through the atmosphere than low condition, solar radiation reaching the surface decreases during daytime. Subsequently, convection and precipitation over land weaken by inducing greater radiative forcing and stability. Therefore, vertical velocity over land (sea) decreases (increases) by inducing low-level wind divergence (convergence), relatively. This results in the successful MJO-envelope that propagates across the MC through more precipitation (fully developing convection) over the sea. The difference in moist static energy (MSE) shows that as the aerosol number concentration increases, less MSE is consumed over land in the high condition than in the low condition during daytime due to the relatively stable environment. The reduced depletion of MSE during daytime amplifies the level of stored energy after this time. This energy induces stronger updraft during nighttime. Peak-phase of diurnal cycle of precipitation over land is moved from late-afternoon (i.e., 17 Local Standard Time (LST)) to midnight (23 LST). This result suggests that the MJO-envelope might be able to propagate through the MC if phase of diurnal cycle over land and sea is the similar pattern (i.e., maximum peak phase over land becomes close to over sea).
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2020
- Bibcode:
- 2020AGUFMA045...10C
- Keywords:
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- 3311 Clouds and aerosols;
- ATMOSPHERIC PROCESSES;
- 3314 Convective processes;
- ATMOSPHERIC PROCESSES;
- 3354 Precipitation;
- ATMOSPHERIC PROCESSES;
- 3359 Radiative processes;
- ATMOSPHERIC PROCESSES