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The Asian summer monsoon Chemical and Climate Impact Project (ACCLIP) used the NSF/NCAR Gulfstream V (GV) research aircraft, the NASA WB-57f research aircraft, the Korean NARA King Air, and a broad set of balloon launches to investigate atmospheric processes that influence ozone depletion and climate in the Korea/Japan region. The WB-57 and NSF GV part of the field campaign was flown from Osan Air Base, Republic of Korea during the July-August 2022 period.This presentation will show some of the dynamical and transport aspects of the Asian summer monsoon anti-cyclone (ASMA) during the summer of 2022. In particular, the strength and flow aspects of the ASMA will be illustrated and shown in the context of an ASMA MERRA-2 climatology. Flight overviews against this flow field will be compared against detrainment events from the ASMA from Asia into the Pacific Ocean. Flight profiles will also show how ACCLIP made extensive sampling of the ASMA’s eastern flank – mapping of the vertical and horizontal structure in the upper troposphere and lower stratosphere.

We implemented the Community Aerosol and Radiation Model for Atmospheres (CARMA) in both the high and low-top model versions of the Community Earth System Model Version 2 (CESM2). CARMA is a sectional microphysical model, which we use for aerosol in both the troposphere and stratosphere. CARMA is fully coupled to chemistry, clouds, radiation, and transport routines in CESM2. This development enables the comparison of simulations with a sectional (CARMA) and a modal (MAM4) aerosol microphysical model in the same modeling framework. The new implementation of CARMA has been adopted from previous work with some additions that align with the current CESM2 MAM4 implementation. The main updates include an interactive secondary organic aerosol description in CARMA using the volatility basis set (VBS) approach, updated wet removal, and the use of transient emissions of aerosols and trace gases. In addition, we implemented an alternative aerosol nucleation scheme in CARMA, which is also used in MAM4. Detailed comparisons of stratospheric aerosol properties after the Mt Pinatubo eruption reveal the importance of prescribing sulfur injections in a larger region rather than in a single column to better represent the observed evolution of aerosols. Both CARMA and MAM4 in CESM2 are able to represent stratospheric and tropospheric aerosol properties reasonably well compared to observations. Several differences in the performance of the two aerosol models show, in general, an improved representation of aerosols using the sectional aerosol model in CESM2. These include a better representation of the aerosol size distribution after the Mt Pinatubo volcanic eruption in CARMA compared to MAM4. MAM4 produces on average smaller aerosols and less removal than CARMA, which results in a larger total mass. Both CARMA and MAM4 reproduce stratospheric Aerosol Optical Depth (AOD) within the errorbar of the observations between 2001 and 2020, except for recent larger volcanic eruptions that are overestimated by both model configurations. The CARMA background surface area density and aerosol size distribution in the stratosphere and troposphere compare well to observations, with some underestimation of the Aitken-mode size range. MAM4 shows shortcomings in reproducing coarse-mode aerosol distributions in the stratosphere and troposphere. This work outlines additional development needs for CESM2 CARMA to improve the model compared to observations in both the troposphere and stratosphere.

This presentation reports the findings of a multi-model pre-mission study in preparation for an airborne field campaign to investigate the upper troposphere and lower stratosphere (UTLS) composition under the influence of the Asian summer monsoon (ASM). The NSF/NASA supported airborne study is planned for the western Pacific atmosphere during July-August 2020 using a base in Okinawa, Japan. The pre-mission study uses three chemistry-transport models (i.e., NASA GSFC GEOS5, NCAR WACCM, and ECMWF CAMS) to investigate transport patterns and gas and aerosol chemical composition in the campaign region UTLS during the 2019 ASM period. In addition, artificial surface tracers from the WRF model helped identify the locations and evolution of rapid convective uplifting from regional sources. The impact of one typhoon occurrence during this 2019 ASM period will be discussed. Together, the multi-model results support the hypotheses of the ACCLIP campaign which identifies the western Pacific as a significant pathway for reactive chemical pollutants and climate relevant emissions from the ASM to enter the global UTLS.

We explore several issues relevant to assessments of solar and infrared radiative effects due to mineral aerosols. One issue is the importance of the vertical distribution of dust for calculations of dust radiative heating rates. Another issue is the role that clouds may play in augmenting the radiative forcing by dust. We also explore the importance of the composition of mineral aerosols by employing spectral optical properties for dust that comes from two different regions of the globe, the Saharan and Afghan deserts. A combined longwave and shortwave radiative transfer model was used to determine the instantaneous radiative forcing in the atmosphere, radiative fluxes at the surface, and radiative heating rates by airborne mineral aerosols for clear-sky and cloudy atmospheric conditions. Extensive calculations with our model show that increasing dust loading results in increasing both solar heating rates and infrared cooling rates. However, the net instantaneous rates during the day are always positive, yielding net radiative heating of the dust layer. With similar atmospheric conditions and dust loading, Saharan dust causes larger heating rates than Afghan dust. The magnitudes of the Saharan dust heating rates can easily be 25% larger than Afghan dust heating rates at high Sun angles and over bright surfaces. Also, Saharan dust yields more positive values of TOA (top of the atmosphere) radiative forcing than Afghan dust; and for a diurnal average, this can lead to a change of sign of the TOA radiative forcing from negative to positive just due to mineralogical composition. Clouds significantly influence the direct radiative impact of dust depending on cloud altitude and optical depth. Moreover, this influence is strongly dependent on Sun position and surface albedo.

[1] We have modeled the effects of moderate-sized (30–100 km diameter) impacts on Mars using a one-dimensional radiative-convective model. The model computes the evolution of temperature following an impact and includes a subsurface model to compute the evolution of the ground temperature; a hydrological cycle to follow the evaporation, condensation, and precipitation of injected and surface-evaporated water; a radiative transfer code to compute greenhouse warming by CO2, water vapor, and water clouds; and an atmospheric thermodynamics module to compute the latent heating due to cloud formation/dissipation. We have found that parts of the Martian regolith may be kept above freezing for 95 days to decades by the modeled events. However, if we include the radiative effects of water clouds, a sustained greenhouse climate is computed for impactors 50 km in size that could be centuries long. The amount of water precipitated out of the atmosphere from vaporization of impactor, target, and polar caps yields global rainfall totals ranging from 40 to 18 m depending on the size of the impactor and assumed background CO2 atmosphere. We also estimate the surface erosion following precipitation events and find that the total erosion done by all impactors in time is the same order of magnitude as the total erosion estimated to have occurred on early Mars.