An examination of summertime transport processes during INTEX-A using meteorological analyses and synthetic MOPITT carbon monoxide retrievals.

摘要

This dissertation consists of two complementary major sections. The first is an examination of summertime cyclone transport processes during NASA's Intercontinental Chemical Transport Experiment (INTEX-A) field campaign during Summer 2004. Warm conveyor belts (WCBs) are important mechanisms for transporting pollution during the cool season. These airstreams distribute surface emissions throughout the troposphere, playing a major role in the long range transport of chemical species.; Previous efforts to understand the lofting of WCBs have not investigated the relative importance of vertical forcing. In this study, we use fine resolution model-derived meteorological data, air parcel trajectories, flux calculations, and a diagnostic package for weather systems to perform a focused investigation of WCBs during the warm season INTEX-A period. Lifting and transport mechanisms during INTEX-A are compared to a well documented cool season WCB case in the literature.; Results show that weak, mid-latitude cyclones are capable of producing vertical transport as great or greater than much stronger cyclones. An analysis of forcing terms contributing to vertical motion reveals that the Laplacian of latent heat release is the primary contributor to vertical motion during some cases of INTEX-A. The latent heating term is found to be greatest in areas of deep convection. This convection allows weak cyclones to produce WCB-like transport.; WCB pathways are similar for the cases studied. In each example, air which originates far south of the low in the warm sector, ascends to the north, and joins the upper-level westerly flow northeast of the low center. Although the transport pathways are similar, the forcing mechanism and location of maximum vertical transport are found to exhibit strong case-to-case variability. When cyclone scale dynamics are relatively weak, widespread deep convection, especially south of the cyclone's center, is necessary to produce transport resembling a WCB.; The second major component of the research is an investigation of warm season carbon monoxide (CO) transport episodes during INTEX-A using synthetic data to simulate CO retrievals from MOPITT's gas correlation radiometers. This was done as if MOPITT was in geosynchronous orbit, providing simultaneous views of CO rather than the much sparser view currently provided by operational MOPITT aboard the polar orbiting Terra satellite. Pollution and its transport are global problems that require space-derived measurements for diagnosis and research. Since CO has a median lifetime of approximately two months, it is a good tracer of tropospheric circulations. This study determines the extent to which space-based MOPITT retrievals describe CO during several meteorological scenarios. Our procedure creates synthetic MOPITT retrievals using CO output from the Sulfur Transport Eulerian Model (STEM) regional scale chemical transport model. That is, STEM-derived CO vertical profiles are imported into a radiative transfer code. The calculated radiation spectra then are input to the MOPITT CO retrieval algorithm to create a synthetic version of MOPITT CO. MOPITT is assumed to be in geostationary orbit, and the effects of clouds are not considered. Simulated imagery is shown to be a valuable tool for understanding the capabilities of current sensors and the potential for new sensors to be placed on different platforms. This type of study would not have been possible using operational retrievals.; We examine three phenomena observed during INTEX-A: Alaskan fires, urban plumes, and a warm conveyor belt. The evolution of thick, broad STEM CO patterns in the mid-troposphere is well represented by the synthetic MOPITT CO retrievals. Due to the MOPITT retrievals having coarse vertical resolution, as well as being constrained by a priori information, differences in the magnitudes of STEM and MOPITT CO were often seen. Neglecting differences in magnitude, MOPITT is shown to be useful at describ