Integrated climate model-oxygen isotope evidence for a North American monsoon during the Late Cretaceous

2010 ◽  
Vol 289 (1-2) ◽  
pp. 11-21 ◽  
Author(s):  
Henry C. Fricke ◽  
Brady Z. Foreman ◽  
Jacob O. Sewall
Keyword(s):  
Oxygen Isotope ◽  
Late Cretaceous ◽  
North American ◽  
Climate Model ◽  
North American Monsoon ◽  
Isotope Evidence

scholarly journals Long-Term Changes in the Climatology of Transient Inverted Troughs over the North American Monsoon Region and Their Effects on Precipitation

2016 ◽  
Vol 29 (17) ◽  
pp. 6037-6064 ◽  
Author(s):  
Timothy M. Lahmers ◽  
Christopher L. Castro ◽  
David K. Adams ◽  
Yolande L. Serra ◽  
John J. Brost ◽  
...  
Keyword(s):  
North American ◽  
Climate Model ◽  
Regional Climate ◽  
Track Density ◽  
North American Monsoon ◽  
Northwest Mexico ◽  
The North ◽  
Simulated Precipitation ◽  
Precipitation Estimates ◽  
Resolution Model

Abstract Transient inverted troughs (IVs) are a trigger for severe weather during the North American monsoon (NAM) in the southwest contiguous United States (CONUS) and northwest Mexico. These upper-tropospheric disturbances enhance the synoptic-scale and mesoscale environment for organized convection, increasing the chances for microbursts, straight-line winds, blowing dust, and flash flooding. This work considers changes in the track density climatology of IVs between 1951 and 2010. IVs are tracked as potential vorticity (PV) anomalies on the 250-hPa surface from a regional climate model that dynamically downscales the NCEP–NCAR Reanalysis 1. Late in the NAM season, a significant increase in IV track density over the 60-yr period is observed over Southern California and western Arizona, coupled with a slight decrease over northwest Mexico. Changes in precipitation are evaluated on days when an IV is observed and days without an IV, using high-resolution model-simulated precipitation estimates and CPC gridded precipitation observations. Because of changes in the spatial distribution of IVs during the 1951–2010 analysis period, which are associated with a strengthening of the monsoon ridge, it is suggested that IVs have played a lesser role in the initiation and organization of monsoon convection in the southwest CONUS during recent warm seasons.

scholarly journals Mechanisms Controlling Precipitation in the Northern Portion of the North American Monsoon

2011 ◽  
Vol 24 (11) ◽  
pp. 2771-2783 ◽  
Author(s):  
Ruth Cerezo-Mota ◽  
Myles Allen ◽  
Richard Jones
Keyword(s):  
Climate Change ◽  
North American ◽  
General Circulation ◽  
Climate Model ◽  
General Circulation Models ◽  
Regional Model ◽  
North American Monsoon ◽  
Low Level ◽  
The North ◽  
Northern Portion

Abstract Key mechanisms important for the simulation and better understanding of the precipitation of the North American monsoon (NAM) were analyzed in this paper. Three experiments with the Providing Regional Climates for Impacts Studies (PRECIS) regional climate model, the Hadley Centre Regional Model version 3P (HadRM3P), driven by different boundary conditions were carried out. After a detailed analysis of the moisture and low-level winds derived from the models, the authors conclude that the Gulf of Mexico (GoM) moisture and the Great Plains low-level jet (GPLLJ) play an important role in the northern portion of the NAM. Moreover, the realistic simulation of these features is necessary for a better simulation of precipitation in the NAM. Previous works suggest that the influence of moisture from the GoM in Arizona–New Mexico (AZNM) takes place primarily via the middle- and upper-tropospheric flow (above 700 mb). However, it is shown here that if the GoM does not supply enough moisture and the GPLLJ at lower levels (below 700 mb) does not reach the AZNM region, then a dry westerly flow dominates that area and the summer precipitation is below normal. The implications of these findings for studies of climate change are demonstrated with the analysis of two general circulation models (GCMs) commonly used for climate change prediction, which are shown not to reproduce correctly the GPLLJ intensity nor the moisture in the GoM. This implies that the precipitation in AZNM would not be correctly represented by a regional model driven by these GCMs.

Towards Assessing NARCCAP Regional Climate Model Credibility for the North American Monsoon: Current Climate Simulations*

2013 ◽  
Vol 26 (22) ◽  
pp. 8802-8826 ◽  
Author(s):  
Melissa S. Bukovsky ◽  
David J. Gochis ◽  
Linda O. Mearns
Keyword(s):  
North American ◽  
Climate Models ◽  
Climate Model ◽  
Global Climate ◽  
Global Climate Model ◽  
Regional Climate ◽  
North American Monsoon ◽  
The North ◽  
Current Climate ◽  
Depth Analysis

Abstract The authors examine 17 dynamically downscaled simulations produced as part of the North American Regional Climate Change Assessment Program (NARCCAP) for their skill in reproducing the North American monsoon system. The focus is on precipitation and the drivers behind the precipitation biases seen in the simulations of the current climate. Thus, a process-based approach to the question of model fidelity is taken in order to help assess confidence in this suite of simulations. The results show that the regional climate models (RCMs) forced with a reanalysis product and atmosphere-only global climate model (AGCM) time-slice simulations perform reasonably well over the core Mexican and southwest United States regions. Some of the dynamically downscaled simulations do, however, have strong dry biases in Arizona that are related to their inability to develop credible monsoon flow structure over the Gulf of California. When forced with different atmosphere–ocean coupled global climate models (AOGCMs) for the current period, the skill of the RCMs subdivides largely by the skill of the forcing or “parent” AOGCM. How the inherited biases affect the RCM simulations is investigated. While it is clear that the AOGCMs have a large influence on the RCMs, the authors also demonstrate where the regional models add value to the simulations and discuss the differential credibility of the six RCMs (17 total simulations), two AGCM time slices, and four AOGCMs examined herein. It is found that in-depth analysis of parent GCM and RCM scenarios can identify a meaningful subset of models that can produce credible simulations of the North American monsoon precipitation.

scholarly journals A 30-Yr Climatology of Meteorological Conditions Associated with Lightning Days in the Interior Western United States

2020 ◽  
Vol 33 (9) ◽  
pp. 3771-3785
Author(s):  
Dmitri A. Kalashnikov ◽  
Paul C. Loikith ◽  
Arielle J. Catalano ◽  
Duane E. Waliser ◽  
Huikyo Lee ◽  
...  
Keyword(s):  
United States ◽  
Great Basin ◽  
North American ◽  
Geopotential Height ◽  
Climate Model ◽  
Warm Season ◽  
Meteorological Conditions ◽  
Western United States ◽  
North American Monsoon ◽  
The North

AbstractA 30-yr climatology of lightning days and associated synoptic meteorological patterns are characterized across the interior western United States (WUS). Locally centered composite analyses show preferred synoptic meteorological patterns with positive 500-hPa geopotential height anomalies located to the northeast and negative sea level pressure anomalies to the northwest and collocated with local lightning days. Variations in preferred patterns for local lightning days are seen across the interior WUS. Areas not commonly affected by the North American monsoon system including the western Great Basin and northern Rocky Mountains show higher-amplitude anomalies of geopotential height, moisture, and midtropospheric instability patterns suggesting the importance of episodic midlatitude dynamics to lightning days in such locations. By contrast, locations closer to the core of the North American monsoon show weaker anomalies, likely reflecting the prevalence of favorable mesoscale dynamics key to lightning production during warm-season months in locations in the interior Southwest. Meteorological patterns for select locations are explored in more detail and two case studies of notably active lightning events are presented. Results from this observational analysis provide a foundation for evaluating meteorological conditions on lightning days in climate model simulations for the interior WUS.

scholarly journals Regional Climate Model Simulation of U.S.–Mexico Summer Precipitation Using the Optimal Ensemble of Two Cumulus Parameterizations

2007 ◽  
Vol 20 (20) ◽  
pp. 5201-5207 ◽  
Author(s):  
Xin-Zhong Liang ◽  
Min Xu ◽  
Kenneth E. Kunkel ◽  
Georg A. Grell ◽  
John S. Kain
Keyword(s):  
Regional Climate Model ◽  
North American ◽  
Climate Model ◽  
Mesoscale Model ◽  
Regional Climate ◽  
Summer Precipitation ◽  
Superior Performance ◽  
North American Monsoon ◽  
Monsoon Region ◽  
Optimal Ensemble

Abstract The fifth-generation Pennsylvania State University–NCAR Mesoscale Model (MM5)-based regional climate model (CMM5) simulations of U.S.–Mexico summer precipitation are quite sensitive to the choice of Grell or Kain–Fritsch convective parameterization. An ensemble based on these two parameterizations provides superior performance because distinct regions exist where each scheme complementarily captures certain observed signals. For the interannual anomaly, the ensemble provides the most significant improvement over the Rockies, Great Plains, and North American monsoon region. For the climate mean, the ensemble has the greatest impact on skill over the southeast United States and North American monsoon region, where CMM5 biases associated with the individual schemes are of opposite sign. Results are very sensitive to the specific methods used to generate the ensemble. While equal weighting of individual solutions provides a more skillful result overall, considerable further improvement is achieved when the weighting of individual solutions is optimized as a function of location.

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