scholarly journals Thunderstorms and upper troposphere chemistry during the early stages of the 2006 North American Monsoon

2012 ◽  
Vol 12 (22) ◽  
pp. 11003-11026 ◽  
Author(s):  
M. C. Barth ◽  
J. Lee ◽  
A. Hodzic ◽  
G. Pfister ◽  
W. C. Skamarock ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Satellite Data ◽  
North American ◽  
Rocky Mountains ◽  
Gulf Coast ◽  
North American Monsoon ◽  
Chemical Production ◽  
Upper Troposphere ◽  
The North

Abstract. To study the meteorology and chemistry that is associated with the early stages of the North American Monsoon, the Weather Research and Forecasting model coupled with Chemistry (WRF-Chem) is applied for the first time at high resolution (4 km grid spacing, allowing for explicit representation of convection) over a large region (continental US and northern Mexico) for a multi-week (15 July to 7 August 2006) integration. Evaluation of model results shows that WRF-Chem reasonably represents the large-scale meteorology and strong convective storms, but tends to overestimate weak convection. In the upper troposphere, the WRF-Chem model predicts ozone (O3) and carbon monoxide (CO) to within 10–20% of aircraft and sonde measurements. Comparison of UT O3 and CO frequency distributions between WRF-Chem and satellite data indicates that WRF-Chem is lofting CO too frequently from the boundary layer (BL). This excessive lofting should also cause biases in the WRF-Chem ozone frequency distribution; however it agrees well with satellite data suggesting that either the chemical production of O3 in the model is overpredicted or there is too much stratosphere to troposphere transport in the model. Analysis of different geographic regions (West Coast, Rocky Mountains, Central Plains, Midwest, and Gulf Coast) reveals that much of the convective transport occurs in the Rocky Mountains, while much of the UT ozone chemical production occurs over the Gulf Coast and Midwest regions where both CO and volatile organic compounds (VOCs) are abundant in the upper troposphere and promote the production of peroxy radicals. In all regions most of the ozone chemical production occurs within 24 h of the air being lofted from the boundary layer. In addition, analysis of the anticyclone and adjacent air indicates that ozone mixing ratios within the anticyclone region associated with the North American Monsoon and just outside the anticyclone are similar. Increases of O3 within the anticyclone are strongly coincident with entrainment of stratospheric air into the anticyclone, but also are from in situ O3 chemical production. In situ O3 production is up to 17% greater within the anticyclone than just outside the anticyclone when the anticyclone is over the southern US indicating that the enhancement of O3 is most pronounced over regions with abundant VOCs.

scholarly journals Thunderstorms and upper troposphere chemistry during the early stages of the 2006 North American Monsoon

2012 ◽  
Vol 12 (7) ◽  
pp. 16407-16455 ◽  
Author(s):  
M. C. Barth ◽  
J. Lee ◽  
A. Hodzic ◽  
G. Pfister ◽  
W. C. Skamarock ◽  
...  
Keyword(s):  
Boundary Layer ◽  
North American ◽  
Rocky Mountains ◽  
Gulf Coast ◽  
North American Monsoon ◽  
Chemical Production ◽  
Upper Troposphere ◽  
Mixing Ratios ◽  
The North

Abstract. In this study, the Weather Research and Forecasting model coupled with Chemistry (WRF-Chem) is applied at 4 km horizontal grid spacing to study the meteorology and chemistry over the continental US and Northern Mexico region for the 15 July to 7 August 2006 period, which coincides with the early stages of the North American Monsoon. Evaluation of model results shows that WRF-Chem reasonably represents the large-scale meteorology and strong convective storms, but tends to overestimate weak convection. In the upper troposphere, the WRF-Chem model predicts ozone and carbon monoxide (CO) to within 10–20% of aircraft and sonde measurements. However, the frequency distribution from satellite data indicates that WRF-Chem is lofting too much CO from the boundary layer (BL). Because ozone mixing ratios agree well with these same satellite data, it suggests that chemical production of O3 in the model is overpredicted and compensates for the excess convective lofting of BL air. Analysis of different geographic regions (West Coast, Rocky Mountains, Central Plains, Midwest, and Gulf Coast) reveals that much of the convective transport occurs in the Rocky Mountains, while much of the UT ozone chemical production occurs over the Gulf Coast and Midwest regions where both CO and volatile organic compounds (VOCs) are abundant in the upper troposphere and promote the production of peroxy radicals. In all regions most of the ozone chemical production occurs within 24 h of the air being lofted from the boundary layer. In addition, analysis of the anticyclone and adjacent air indicates that ozone mixing ratios within the anticyclone region associated with the North American Monsoon and just outside the anticyclone are similar. Increases of O3 within the anticyclone are strongly coincident with entrainment of stratospheric air into the anticyclone, but also are from in situ O3 chemical production. In situ O3 production is up to 17% greater within the anticyclone than just outside the anticyclone when the anticyclone is over the Southern US indicating that the enhancement of O3 is most pronounced over regions with abundant VOCs.

scholarly journals Vertical Structure of Precipitation and Related Microphysics Observed by NOAA Profilers and TRMM during NAME 2004

2007 ◽  
Vol 20 (9) ◽  
pp. 1693-1712 ◽  
Author(s):  
Christopher R. Williams ◽  
Allen B. White ◽  
Kenneth S. Gage ◽  
F. Martin Ralph
Keyword(s):  
North American ◽  
Vertical Structure ◽  
Gulf Coast ◽  
Tropical Rainfall Measuring Mission ◽  
North American Monsoon ◽  
Field Site ◽  
Stratiform Rain ◽  
Bright Band ◽  
The North ◽  
Raindrop Size Distribution

Abstract In support of the 2004 North American Monsoon Experiment (NAME) field campaign, NOAA established and maintained a field site about 100 km north of Mazatlán, Mexico, consisting of wind profilers, precipitation profilers, surface upward–downward-looking radiometers, and a 10-m meteorological tower to observe the environment within the North American monsoon. Three objectives of this NOAA project are discussed in this paper: 1) to observe the vertical structure of precipitating cloud systems as they passed over the NOAA profiler site, 2) to estimate the vertical air motion and the raindrop size distribution from near the surface to just below the melting layer, and 3) to better understand the microphysical processes associated with stratiform rain containing well-defined radar bright bands. To provide a climatological context for the profiler observations at the field site, the profiler reflectivity distributions were compared with Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar (PR) reflectivity distributions from the 2004 season over the NAME domain as well as from the 1998–2005 seasons. This analysis places the NAME 2004 observations into the context of other monsoon seasons. It also provides a basis for evaluating the representativeness of the structure of the precipitation systems sampled at this location. The number of rain events observed by the TRMM PR is dependent on geography; the land region, which includes portions of the Sierra Madre Occidental, has more events than the coast and gulf regions. Conversely, from this study it is found that the frequencies of occurrence of stratiform rain and reflectivity profiles with radar bright bands are mostly independent of region. The analysis also revealed that the reflectivity distribution at each height has more year-to-year variability than region-to-region variability. These findings suggest that in cases with a well-defined bright band, the vertical profile of the reflectivity relative to the height of the bright band is similar over the gulf, coast, and land regions.

Investigating the roles of the Asian monsoon, the North American monsoon, and Hurricanes for efficient transport of chlorinated short-lived species to the UTLS based on in situ observations

2021 ◽  
Author(s):  
Valentin Lauther ◽  
Johannes Wintel ◽  
Emil Gerhardt ◽  
Andrea Rau ◽  
Peter Hoor ◽  
...  
Keyword(s):  
High Altitude ◽  
Central America ◽  
North American ◽  
Asian Summer Monsoon ◽  
North American Monsoon ◽  
Mixing Ratios ◽  
The North ◽  
Asian Summer ◽  
Efficient Transport

<p>Chlorinated very short-lived substances (Cl-VSLS) are not controlled by the Montreal Protocol but the recent emission increase of the Cl-VSLS CH<sub>2</sub>Cl<sub>2</sub> (Dichloromethane) and CHCl<sub>3</sub> (Chloroform) is believed to significantly increase the stratospheric chlorine loading from VSLS. Provided efficient transport of Cl-VSLS from the source region into the stratosphere further emission increases could ultimately even cause a significant delay of the predicted recovery date of the ozone layer to pre-1980 values. During the WISE (Wave-driven ISentropic Exchange) campaign in autumn 2017 excessive probing of the UTLS (upper troposphere lower stratosphere) region above Western Europe and the Atlantic Ocean was conducted from aboard the HALO (High Altitude and Long range) research aircraft. We use real-time in situ WISE measurements of CH<sub>2</sub>Cl<sub>2</sub> and CHCl<sub>3</sub> from HAGAR-V (High Altitude Gas AnalyzeR – 5 channel version) in correlation with N<sub>2</sub>O from UMAQS (University of Mainz Airborne QCL Spectrometer), as well as CLaMS (Chemical Lagrangian Model of the Stratosphere) global 3-dimensional simulations of air mass origin tracers and backward trajectories to identify the most efficient transport mechanisms for Cl-VSLS entering the LS region in northern hemispheric summer.</p><p>The WISE measurements reveal two distinct transport pathways into the UTLS region of particularly CH<sub>2</sub>Cl<sub>2</sub>-rich and CH<sub>2</sub>Cl<sub>2</sub>-poor air. CH<sub>2</sub>Cl<sub>2</sub>-rich air could be identified to be transported by the Asian summer monsoon within about 4-10 weeks from its source regions in Asia into the stratosphere above the Atlantic Ocean at around 380 K and above. CH<sub>2</sub>Cl<sub>2</sub>-poor air could be identified to be mainly uplifted to potential temperatures of about 365 K by the North American monsoon above the region of Central America with transport times of only 2-5 weeks. In addition, we could link backward trajectories of CH<sub>2</sub>Cl<sub>2</sub>-poor air in the LS region to be uplifted by the category 5 hurricane Maria in September 2017. Based on all analyzed WISE measurements, we found that almost all young (transport time < 4 months) air masses were uplifted either above Asia or above Central America, emphasizing not only the impact of the Asian summer monsoon on the stratospheric tracer distribution but also that of the North American monsoon and hurricanes.</p><p>The measurements of both CH<sub>2</sub>Cl<sub>2</sub> and CHCl<sub>3</sub> show the lowest stratospheric mixing ratios originating in the region of Central America and enhanced mixing ratios from Asia (enhancements > 100 % and > 50 %, respectively). However, the source distribution of CHCl<sub>3</sub> is much less clear than that of CH<sub>2</sub>Cl<sub>2</sub> and inconspicuous CH<sub>2</sub>Cl<sub>2</sub> measurements can also contain enhanced CHCl<sub>3</sub> mixing ratios. Nevertheless, the anthropogenic impact on CHCl<sub>3</sub> -rich air from Asia is clearly visible in the measurements and we believe it is likely that a future increase of Asian CHCl<sub>3</sub> emissions could lead to similarly large stratospheric enhancements as already observed for CH<sub>2</sub>Cl<sub>2</sub>. Consequently, this would further increase ozone depletion from stratospheric chlorine deposition of VSLS.</p>

scholarly journals Lightning in the North American Monsoon: An Exploratory Climatology

2015 ◽  
Vol 143 (5) ◽  
pp. 1970-1977 ◽  
Author(s):  
Ronald L. Holle ◽  
Martin J. Murphy
Keyword(s):  
Satellite Data ◽  
North American ◽  
Gulf Of California ◽  
Detection Efficiency ◽  
Monsoon Season ◽  
North American Monsoon ◽  
Lightning Stroke ◽  
The North ◽  
Spatial Coverage ◽  
Northwestern Mexico

Abstract Temporal and spatial distributions of the North American monsoon have been studied previously with rainfall and satellite data. In the current study, the monsoon is examined with lightning data from Vaisala’s Global Lightning Dataset (GLD360). GLD360 has been operating for over three years and provides sufficient data to develop an exploratory climatology with minimal spatial variation in detection efficiency and location accuracy across the North American monsoon region. About 80% of strokes detected by GLD360 are cloud to ground. This paper focuses on seasonal, monthly, and diurnal features of lightning occurrence during the monsoon season from Mazatlán north-northwest to northern Arizona and New Mexico. The goal is to describe thunderstorm frequency with a dataset that provides uniform spatial coverage at a resolution of 2–5 km and uniform temporal coverage with individual lightning events resolved to the millisecond, compared with prior studies that used hourly point rainfall or satellite data with a resolution of several kilometers. The monthly lightning stroke density over northwestern Mexico increases between May and June, as thunderstorms begin over the high terrain east of the Gulf of California. The monthly lightning stroke density over the entire region increases dramatically to a maximum in July and August. The highest stroke densities observed in Mexico approach those observed by GLD360 in subtropical and tropical regions in Africa, Central and South America, and Southeast Asia. The diurnal cycle of lightning exhibits a maximum over the highest terrain near noon, associated with daytime solar heating, a maximum near midnight along the southern coast of the Gulf, and a gradual decay toward sunrise.

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