scholarly journals Quantifying the impact of the North American monsoon and deep midlatitude convection on the subtropical lowermost stratosphere using in situ measurements

2007 ◽  
Vol 112 (D18) ◽  
Author(s):  
E. M. Weinstock ◽  
J. V. Pittman ◽  
D. S. Sayres ◽  
J. B. Smith ◽  
J. G. Anderson ◽  
...  
Keyword(s):  
North American ◽  
In Situ Measurements ◽  
North American Monsoon ◽  
The North ◽  
The Impact

scholarly journals The North American Monsoon GPS Transect Experiment 2013

2016 ◽  
Vol 97 (11) ◽  
pp. 2103-2115 ◽  
Author(s):  
Yolande L. Serra ◽  
David K. Adams ◽  
Carlos Minjarez-Sosa ◽  
James M. Moker ◽  
Avelino F. Arellano ◽  
...  
Keyword(s):  
Water Vapor ◽  
North American ◽  
Water Cycle ◽  
Precipitable Water ◽  
Annual Rainfall ◽  
North American Monsoon ◽  
Atmospheric Sciences ◽  
The North ◽  
Northwestern Mexico ◽  
The Impact

Abstract Northwestern Mexico experiences large variations in water vapor on seasonal time scales in association with the North American monsoon, as well as during the monsoon associated with upper-tropospheric troughs, mesoscale convective systems, tropical easterly waves, and tropical cyclones. Together these events provide more than half of the annual rainfall to the region. A sufficient density of meteorological observations is required to properly observe, understand, and forecast the important processes contributing to the development of organized convection over northwestern Mexico. The stability of observations over long time periods is also of interest to monitor seasonal and longer-time-scale variability in the water cycle. For more than a decade, the U.S. Global Positioning System (GPS) has been used to obtain tropospheric precipitable water vapor (PWV) for applications in the atmospheric sciences. There is particular interest in establishing these systems where conventional operational meteorological networks are not possible due to the lack of financial or human resources to support the network. Here, we provide an overview of the North American Monsoon GPS Transect Experiment 2013 in northwestern Mexico for the study of mesoscale processes and the impact of PWV observations on high-resolution model forecasts of organized convective events during the 2013 monsoon. Some highlights are presented, as well as a look forward at GPS networks with surface meteorology (GPS-Met) planned for the region that will be capable of capturing a wider range of water vapor variability in both space and time across Mexico and into the southwestern United States.

scholarly journals Comments on “Regional Impacts of Irrigation in Mexico and the Southwestern United States on Hydrometeorological Fields in the North American Monsoon Region”

2018 ◽  
Vol 19 (2) ◽  
pp. 477-481 ◽  
Author(s):  
Theodore J. Bohn ◽  
Enrique R. Vivoni
Keyword(s):  
North American ◽  
Gulf Of California ◽  
Wrf Model ◽  
Summer Precipitation ◽  
Atmospheric Modeling ◽  
Irrigated Agriculture ◽  
North American Monsoon ◽  
Impact Surface ◽  
The North ◽  
The Impact

Abstract For their investigation of the impact of irrigated agriculture on hydrometeorological fields in the North American monsoon (NAM) region, Mahalov et al. used the Weather Research and Forecasting (WRF) Model to simulate weather over the NAM region in the summer periods of 2000 and 2012, with and without irrigation applied to the regional croplands. Unfortunately, while the authors found that irrigated agriculture may indeed influence summer precipitation, the magnitude, location, and seasonality of their irrigation inputs were substantially inaccurate because of 1) the assumption that pixels classified as “irrigated cropland” are irrigated during the summer and 2) an outdated land cover map that misrepresents known agricultural districts. The combined effects of these errors are 1) an overestimation of irrigated croplands by a factor of 3–10 along the coast of the Gulf of California and by a factor of 1.5 near the Colorado River delta and 2) a large underestimation of irrigation by a factor of 7–10 in Chihuahua, particularly in 2012. Given the sensitivity of the WRF simulations conducted by Mahalov et al. to the presence of irrigated agriculture, it is expected that the identified errors would significantly impact surface moisture and energy fluxes, resulting in noticeably different effects on precipitation. The authors suggest that the analysis of irrigation effects on precipitation using coupled land–atmospheric modeling systems requires careful specification of the spatiotemporal distribution of irrigated croplands.

Impact of Tropical Easterly Waves on the North American Monsoon

2007 ◽  
Vol 20 (7) ◽  
pp. 1219-1238 ◽  
Author(s):  
Jennifer L. Adams ◽  
David J. Stensrud
Keyword(s):  
United States ◽  
Boundary Conditions ◽  
North American ◽  
Moisture Flux ◽  
North American Monsoon ◽  
Southern Plains ◽  
The North ◽  
Gulf Surges ◽  
Northwestern Mexico ◽  
The Impact

Abstract The North American monsoon (NAM) is a prominent summertime feature over northwestern Mexico and the southwestern United States. It is characterized by a distinct shift in midlevel winds from westerly to easterly as well as a sharp, marked increase in rainfall. This maximum in rainfall accounts for 60%–80% of the annual precipitation in northwestern Mexico and nearly 40% of the yearly rainfall over the southwestern United States. Gulf surges, or coastally trapped disturbances that occur over the Gulf of California, are important mechanisms in supplying the necessary moisture for the monsoon and are hypothesized in previous studies to be initiated by the passage of a tropical easterly wave (TEW). Since the actual number of TEWs varies from year to year, it is possible that TEWs are responsible for producing some of the interannual variability in the moisture flux and rainfall seen in the NAM. To explore the impact of TEWs on the NAM, four 1-month periods are chosen for study that represent a reasonable variability in TEW activity. Two continuous month-long simulations are produced for each of the selected months using the Pennsylvania State University–National Center for Atmospheric Research Mesoscale Model. One simulation is a control run that uses the complete boundary condition data, whereas a harmonic analysis is used to remove TEWs with periods of approximately 3.5 to 7.5 days from the model boundary conditions in the second simulation. These simulations with and without TEWs in the boundary conditions are compared to determine the impact of the waves on the NAM. Fields such as meridional moisture flux, rainfall totals, and surge occurrences are examined to define similarities and differences between the model runs. Results suggest that the removal of TEWs not only reduces the strength of gulf surges, but also rearranges rainfall over the monsoon region. Results further suggest that TEWs influence rainfall over the Southern Plains of the United States, with TEWs leading to less rainfall in this region. While these results are only suggestive, since rainfall is the most difficult model forecast parameter, it may be that TEWs alone can explain part of the inverse relationship between NAM and Southern Plains rainfall.

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 The impact of sea surface temperature on the North American monsoon: A GCM study

2003 ◽  
Vol 30 (2) ◽  
Author(s):  
Zong-Liang Yang ◽  
Dave Gochis ◽  
William James Shuttleworth ◽  
Guo-Yue Niu
Keyword(s):  
Surface Temperature ◽  
Sea Surface Temperature ◽  
North American ◽  
Sea Surface ◽  
North American Monsoon ◽  
The North ◽  
The Impact

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.

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