Abstract:The National Oceanic and Atmospheric Administration's National Environmental Satellite Data and Information Service (NOAA/NESDIS) Interactive Multisensor Snow and Ice Mapping System (IMS) has undergone substantial changes since its inception in 1997. These changes include the data sources used to generate the product, methodology of product creation, and even changes in the output. Among the most notable of the past upgrades to the IMS are a 4-km resolution grid output, ingest of an automated snow detection algorithm, expansion to a global extent, and a static Digital Elevation Model for mapping based on elevation. Further developments to this dynamic system will continue as NOAA strives to improve snow parameterization for weather forecast modeling. Several future short-term enhancements will be evaluated for possible transition to operations before the Northern Hemisphere winter of 2006-2007. Current and historical data will be adopted to a geographic information systems (GIS) format before 2007, as well. Longer-term enhancements are also planned to account for new snow data sources, mapping methodologies and user requirements. These modifications are being made with care to preserve the integrity of the long-standing satellite-derived snow record that is vital to global change detection. Published in 2007 by John Wiley & Sons, Ltd.

A series of large mesoscale convective systems that occurred during the Brazilian phase of GTE/TRACE A (Transport and Atmospheric Chemistry near the Equator‐Atlantic) provided an opportunity to observe deep convective transport of trace gases from biomass burning. This paper reports a detailed analysis of flight 6, on September 27, 1992, which sampled cloud‐ and biomass‐burning‐perturbed regions north of Brasilia. High‐frequency sampling of cloud outflow at 9–12 km from the NASA DC‐8 showed enhancement of CO mixing ratios typically a factor of 3 above background (200–300 parts per billion by volume (ppbv) versus 90 ppbv) and significant increases in NOx and hydrocarbons. Clear signals of lightning‐generated NO were detected; we estimate that at least 40% of NOx at the 9.5‐km level and 32% at 11.3 km originated from lightning. Four types of model studies have been performed to analyze the dynamical and photochemical characteristics of the series of convective events. (1) Regional simulations for the period have been performed with the NCAR/Penn State mesoscale model (MM5), including tracer transport of carbon monoxide, initialized with observations. Middle‐upper tropospheric enhancements of a factor of 3 above background are reproduced. (2) A cloud‐resolving model (the Goddard cumulus ensemble (GCE) model) has been run for one representative convective cell during the September 26–27 episode. (3) Photochemical calculations (the Goddard tropospheric chemical model), initialized with trace gas observations (e.g., CO, NOx, hydrocarbons, O3) observed in cloud outflow, show appreciable O3 formation postconvection, initially up to 7–8 ppbv O3/d. (4) Forward trajectories from cloud outflow levels (postconvective conditions) put the ozone‐producing air masses in eastern Brazil and the tropical Atlantic within 2–4 days and over the Atlantic, Africa, and the Indian Ocean in 6–8 days. Indeed, 3–4 days after the convective episode (September 30, 1992), upper tropospheric levels in the Natal ozone sounding show an average increase of ∼30 ppbv (3 Dobson units (DU) integrated) compared to the September 28 sounding. Our simulated net O3 production rates in cloud outflow are a factor of 3 or more greater than those in air undisturbed by the storms. Integrated over the 8‐ to 16‐km cloud outflow layer, the postconvection net O3 production (∼5–6 DU over 8 days) accounts for ∼25% of the excess O3 (15–25 DU) over the South Atlantic. Comparison of TRACE A Brazilian ozonesondes and the frequency of deep convection with climatology [Kirchhoff et al., this issue] suggests that the late September 1992 conditions represented an unusually active period for both convection and upper tropospheric ozone formation.

The seasonal tropospheric ozone maximum in the tropical South Atlantic, first recognized from satellite observations [Fishman et al., 1986, 1991], gave rise to the IGAC/STARE/SAFARI 1992/TRACE A campaigns (International Global Atmospheric Chemistry/South Tropical Atlantic Regional Experiment/Southern African Atmospheric Research Initiative/Transport and Atmospheric Chemistry Near the Equator‐Atlantic) in September and October 1992. Along with a new TOMS‐based method for deriving tropospheric column ozone, we used the TRACE A/SAFARI 1992 data set to put together a regional picture of the O3 distribution during this period. Sondes and aircraft profiling showed a troposphere with layers of high O3 (≥90 ppbv) all the way to the tropopause. These features extend in a band from 0° to 25°S, over the SE Indian Ocean, Africa, the Atlantic, and eastern South America. A combination of trajectory and photochemical modeling (the Goddard (GSFC) isentropic trajectory and tropospheric point model, respectively) shows a strong connection between regions of high ozone and concentrated biomass burning, the latter identified using satellite‐derived fire counts [Justice et al., this issue]. Back trajectories from a high‐O3 tropical Atlantic region (column ozone at Ascension averaged 50 Dobson units (DU)) and forward trajectories from fire‐rich and convectively active areas show that the Atlantic and southern Africa are supplied with O3 and O3‐forming trace gases by midlevel easterlies and/or recirculating air from Africa, with lesser contributions from South American burning and urban pollution. Limited sampling in the mixed layer over Namibia shows possible biogenic sources of NO. High‐level westerlies from Brazil (following deep convective transport of ozone precursors to the upper troposphere) dominate the upper tropospheric O3 budget over Natal, Ascension, and Okaukuejo (Namibia), although most enhanced O3 (75% or more) equatorward of 10°S was from Africa. Deep convection may be responsible for the timing of the seasonal tropospheric O3 maximum: Natal and Ascension show a 1‐ to 2‐month lag relative to the period of maximum burning [cf. Baldy et al., this issue; Olson et al., this issue]. Photochemical model calculations constrained with TRACE A and SAFARI airborne observations of O3 and O3 precursors (NOx, CO, hydrocarbons) show robust ozone formation (up to 15 ppbv O3/d or several DU/d) in a widespread, persistent, and well‐mixed layer to 4 km. Slower but still positive net O3 formation took place throughout the tropical upper troposphere [cf. Pickering et al., this issue (a); Jacob et al., this issue]. Thus whether it is faster rates of O3 formation in source regions with higher turnover rates or slower O3 production in long‐lived stable layers ubiquitous in the TRACE A region, 10–30 DU tropospheric O3 above a ∼25‐DU background can be accounted for. In summary, the O3 maximum studied in October 1992 was caused by a coincidence of abundant O3 precursors from biomass fires, a long residence time of stable air parcels over the eas...

Photochemical modeling and analysis of field data have been used to evaluate the effects of convective clouds on tropospheric trace gas chemistry. Observations were made during a 1985 field campaign over the rural south-central United States. Meteorological data and measurements of CO, NO, NOy, 03, and hydrocarbons were collected in air surrounding and inside clouds during and immediately following cloud convection. A one-dimensional photochemical model has been used to calculate 03 production potential before and after cloud redistribution of 03 precursor gases. Four distinct types of convective events have been analyzed. Fair weather cumulus clouds increase 03 production in a layer immediately above the boundary layer (to 4 km in the case studied). Outflow from deeper convection can cause enhanced 03 production in the upper troposphere hundreds of kilometers downstream from the clouds. A comparison of trace gas profiles measured in and around a large cumulonimbus during dissipation shows 03 production in the upper troposphere may be increased fourfold by convection relative to undisturbed air. Convective enhancement of 03 production for the entire tropospheric column is about 50%. Compared to nonurban continental regions with no convection, the rate of 03 production potential in air processed by convection is up to 3-4 times greater. Catalysis of 03 production becomes more efficient when NO becomes more dilute after being transported from the boundary layer to the free troposphere. Free tropospheric NO may also be enhanced by lightning, adding to 03 production, particularly when sufficient hydrocarbons are transported to such locations. INTRODUCTION Convective clouds are effective in rapidly transporting trace gases (e.g., CO, NOx, and hydrocarbons) generated in the boundary layer to the free troposphere [Dickerson et al., 1987; Ching and Alkezweeny, 1986; Greenhut, 1986]. Models [e.g., Gidel, 1983; Chatfield and Crutzen, 1984; Costen et al., 1988; Cho et al., 1989] that simulate this vertical transport indicate that convective clouds are capable of transporting and redistributing significant quantities of trace species in the atmosphere. These analyses, however, did not consider the consequences for ozone production resulting from the redistributed trace gases.During convective transport, trace gas concentrations become more dilute through turbulent mixing, and ozone can be produced at a greater rate because NOx catalyzes ozone production more efficiently on a per molecule basis at low concentrations (but greater than 5-10 ppt) than at higher concentrations [Liu et al., 1987]. Therefore photochemical production of ozone can be enhanced during and following convective activity, not only near convection but also in areas downwind of the convective cell. We have reported trace gas observations conducted during and after a series of convective events in June 1985 over rural areas of the south-central United States [Dickerson etPaper number 90JD00777. 0148-0227/90/90JD-00777505.00 Pickering et al., 1988Pickering et...