Changes in Water Vapor Transport and the Production of Precipitation in the Eastern Fertile Crescent as a Result of Global Warming

2008 ◽  
Vol 9 (6) ◽  
pp. 1390-1401 ◽  
Author(s):  
J. P. Evans
Keyword(s):  
Global Warming ◽  
Water Vapor ◽  
Climate Model ◽  
Mesoscale Model ◽  
Regional Climate ◽  
Water Vapor Transport ◽  
State University ◽  
Storm Events ◽  
Fertile Crescent ◽  
Emissions Scenarios

Abstract This study investigates changes in the types of storm events occurring in the Fertile Crescent as a result of global warming. Regional climate model [fifth-generation Pennsylvania State University–National Center for Atmospheric Research Mesoscale Model (MM5)–Noah] simulations are run for the first and last five years of the twenty-first century following the Special Report on Emissions Scenarios (SRES) A2 experiment. Then the precipitation events are classified according to the water vapor fluxes that created them. At present most of the region’s precipitation is from westerly water vapor fluxes. Results indicate that the region will increasingly get its precipitation from large events that are dominated by southerly water vapor fluxes. The increase in these events will occur in the transition seasons, especially autumn.

Response of Seasonal Simulations of a Regional Climate Model to High-Frequency Variability of Soil Moisture during the Summers of 1988 and 1993

2007 ◽  
Vol 8 (4) ◽  
pp. 738-757 ◽  
Author(s):  
Song Yang ◽  
S-H. Yoo ◽  
R. Yang ◽  
K. E. Mitchell ◽  
H. van den Dool ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Water Vapor ◽  
Diurnal Cycle ◽  
High Frequency ◽  
Large Scale ◽  
Climate Model ◽  
Regional Climate ◽  
Water Vapor Transport ◽  
Diurnal Variability ◽  
High Frequency Variability

Abstract This study employs the NCEP Eta Regional Climate Model to investigate the response of the model’s seasonal simulations of summer precipitation to high-frequency variability of soil moisture. Specifically, it focuses on the response of model precipitation and temperature over the U.S. Midwest and Southeast to imposed changes in the diurnal and synoptic variability of soil moisture in 1988 and 1993. High-frequency variability of soil moisture increases (decreases) precipitation in the 1988 drought (1993 flood) year in the central and southern-tier states, except along the Gulf Coast, but causes smaller changes in precipitation along the northern-tier states. The diurnal variability and synoptic variability of soil moisture produce similar patterns of precipitation change, indicating the importance of the diurnal cycle of land surface process. The increase (decrease) in precipitation is generally accompanied by a decrease (increase) in surface and lower-tropospheric temperatures, and the changes in precipitation and temperature are attributed to both the local effect of evaporation feedback and the remote influence of large-scale water vapor transport. The precipitation increase and temperature decrease in 1988 are accompanied by an increase in local evaporation and, more importantly, by an increase in the large-scale water vapor convergence into the Midwest and Southeast. Analogous but opposite-sign behavior occurs in 1993 (compared to 1988) in changes in precipitation, temperature, soil moisture, evaporation, and large-scale water vapor transport. Results also indicate that, in regions where the model simulates the diurnal cycle of soil moisture reasonably well, including this diurnal cycle in the simulations improves model performance. However, no notable improvement in model precipitation can be found in regions where the model fails to realistically simulate the diurnal variability of soil moisture.

Water Vapor Transport and the Production of Precipitation in the Eastern Fertile Crescent

2006 ◽  
Vol 7 (6) ◽  
pp. 1295-1307 ◽  
Author(s):  
J. P. Evans ◽  
R. B. Smith
Keyword(s):  
Water Vapor ◽  
Land Surface ◽  
Clustering Algorithm ◽  
Mesoscale Model ◽  
Water Vapor Transport ◽  
Surface Model ◽  
Precipitation Pattern ◽  
Total Precipitation ◽  
Fertile Crescent ◽  
Precipitation Events

Abstract The study presented here attempts to quantify the significance of southerly water vapor fluxes on precipitation occurring in the eastern Fertile Crescent region. The water vapor fluxes were investigated at high temporal and spatial resolution by using a Regional Climate Model [fifth-generation Pennsylvania State University–NCAR Mesoscale Model (MM5)–Noah land surface model] to downscale the NCEP–NCAR reanalysis. Using the Iterative Self-Organizing Data Analysis Techniques (ISODATA) clustering algorithm, the 200 largest precipitation events, occurring from 1990 through 1994, were grouped into classes based on the similarity of their water vapor fluxes. Results indicate that, while southerly fluxes were dominant in 24% of tested events, these events produced 43% of the total precipitation produced by the 200 largest events. Thus, while the majority of precipitation events occurring in the Fertile Crescent involve significant water vapor advected from the west, those events that included southerly fluxes produced much larger precipitation totals. This suggests that changes that affect these southerly fluxes more than the westerly fluxes (e.g., changes in the Indian monsoon, movement of the head of the Persian Gulf, etc.) may have a relatively strong affect on the total precipitation falling in the Fertile Crescent even though they affect relatively few precipitation events. To obtain a clearer view of the precipitation mechanisms, the authors used a linear model, along with the estimated water vapor fluxes, to downscale from 25 to 1 km. The result shows a spectrum of mountain scales not seen in the regional model, exerting tight control on the precipitation pattern.

scholarly journals 2 °C vs. High Warming: Transitions to Flood-Generating Mechanisms across Canada

Water ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 1494
Author(s):  
Bernardo Teufel ◽  
Laxmi Sushama
Keyword(s):  
Climate Change ◽  
Global Warming ◽  
Climate Model ◽  
Regional Climate ◽  
Adaptation Measures ◽  
Relative Contribution ◽  
Late 21St Century ◽  
Transient Climate Change ◽  
Projected Changes ◽  
Change Mitigation

Fluvial flooding in Canada is often snowmelt-driven, thus occurs mostly in spring, and has caused billions of dollars in damage in the past decade alone. In a warmer climate, increasing rainfall and changing snowmelt rates could lead to significant shifts in flood-generating mechanisms. Here, projected changes to flood-generating mechanisms in terms of the relative contribution of snowmelt and rainfall are assessed across Canada, based on an ensemble of transient climate change simulations performed using a state-of-the-art regional climate model. Changes to flood-generating mechanisms are assessed for both a late 21st century, high warming (i.e., Representative Concentration Pathway 8.5) scenario, and in a 2 °C global warming context. Under 2 °C of global warming, the relative contribution of snowmelt and rainfall to streamflow peaks is projected to remain close to that of the current climate, despite slightly increased rainfall contribution. In contrast, a high warming scenario leads to widespread increases in rainfall contribution and the emergence of hotspots of change in currently snowmelt-dominated regions across Canada. In addition, several regions in southern Canada would be projected to become rainfall dominated. These contrasting projections highlight the importance of climate change mitigation, as remaining below the 2 °C global warming threshold can avoid large changes over most regions, implying a low likelihood that expensive flood adaptation measures would be necessary.

scholarly journals Impacts of 1.5 and 2.0 °C Global Warming on Water Balance Components over Senegal in West Africa

Atmosphere ◽  
2019 ◽  
Vol 10 (11) ◽  
pp. 712
Author(s):  
Mamadou Lamine Mbaye ◽  
Mouhamadou Bamba Sylla ◽  
Moustapha Tall
Keyword(s):  
Global Warming ◽  
West Africa ◽  
Water Deficit ◽  
Climate Model ◽  
Regional Climate ◽  
Climate Change Impacts ◽  
Water Balance Components ◽  
Global Mean Temperature ◽  
The Future ◽  
Annual Water

This study assesses the changes in precipitation (P) and in evapotranspiration (ET) under 1.5 °C and 2.0 °C global warming levels (GWLs) over Senegal in West Africa. A set of twenty Regional Climate Model (RCM) simulations within the Coordinated Regional Downscaling Experiment (CORDEX) following the Representative Concentration Pathways (RCP) 4.5 emission scenario is used. Annual and seasonal changes are computed between climate simulations under 1.5 °C and 2.0 °C warming, with respect to 0.5 °C warming, compared to pre-industrial levels. The results show that annual precipitation is likely to decrease under both magnitudes of warming; this decrease is also found during the main rainy season (July, August, September) only and is more pronounced under 2 °C warming. All reference evapotranspiration calculations, from Penman, Hamon, and Hargreaves formulations, show an increase in the future under the two GWLs, except annual Penman evapotranspiration under the 1.5 °C warming scenario. Furthermore, seasonal and annual water balances (P-ET) generally exhibit a water deficit. This water deficit (up to 180 mm) is more substantial with Penman and Hamon under 2 °C. In addition, analyses of changes in extreme precipitation reveal an increase in dry spells and a decrease in the number of wet days. However, Senegal may face a slight increase in very wet days (95th percentile), extremely wet days (99th), and rainfall intensity in the coming decades. Therefore, in the future, Senegal may experience a decline in precipitation, an increase of evapotranspiration, and a slight increase in heavy rainfall. Such changes could have serious consequences (e.g., drought, flood, etc.) for socioeconomic activities. Thus, strong governmental politics are needed to restrict the global mean temperature to avoid irreversible negative climate change impacts over the country. The findings of this study have contributed to a better understanding of local patterns of the Senegal hydroclimate under the two considered global warming scenarios.

The Mesoscale Response to Global Warming over the Pacific Northwest Evaluated Using a Regional Climate Model Ensemble

2021 ◽  
pp. 1-56
Keyword(s):  
Global Warming ◽  
Pacific Northwest ◽  
Climate Models ◽  
Climate Model ◽  
Regional Climate ◽  
Wrf Model ◽  
Regional Climate Models ◽  
Winter Precipitation ◽  
Historical Period ◽  
Continental Interior

This paper describes the downscaling of an ensemble of twelve GCMs using the WRF model at 12-km grid spacing over the period 1970-2099, examining the mesoscale impacts of global warming as well as the uncertainties in its mesoscale expression. The RCP 8.5 emissions scenario was used to drive both global and regional climate models. The regional climate modeling system reduced bias and improved realism for a historical period, in contrast to substantial errors for the GCM simulations driven by lack of resolution. The regional climate ensemble indicated several mesoscale responses to global warming that were not apparent in the global model simulations, such as enhanced continental interior warming during both winter and summer as well as increasing winter precipitation trends over the windward slopes of regional terrain, with declining trends to the lee of major barriers. During summer there is general drying, except to the east of the Cascades. April 1 snowpack declines are large over the lower to middle slopes of regional terrain, with small snowpack increases over the lower elevations of the interior. Snow-albedo feedbacks are very different between GCM and RCM projections, with the GCM’s producing large, unphysical areas of snowpack loss and enhanced warming. Daily average winds change little under global warming, but maximum easterly winds decline modestly, driven by a preferential sea level pressure decline over the continental interior. Although temperatures warm continuously over the domain after approximately 2010, with slight acceleration over time, occurrences of temperature extremes increase rapidly during the second half of the 21st century.

scholarly journals The Impact of the Sierra Nevada on Low-Level Winds and Water Vapor Transport

2007 ◽  
Vol 8 (4) ◽  
pp. 790-804 ◽  
Author(s):  
Jinwon Kim ◽  
Hyun-Suk Kang
Keyword(s):  
Water Vapor ◽  
Sierra Nevada ◽  
Climate Model ◽  
Northern Region ◽  
Vapor Transport ◽  
Water Vapor Transport ◽  
Western Slope ◽  
Mountain Range ◽  
Low Level ◽  
The Impact

Abstract To understand the influence of the Sierra Nevada on the water cycle in California the authors have analyzed low-level winds and water vapor fluxes upstream of the mountain range in regional climate model simulations. In a low Froude number (Fr) regime, the upstream low-level wind disturbances are characterized by the rapid weakening of the crosswinds and the appearance of a stagnation point over the southwestern foothills. The weakening of the low-level inflow is accompanied by the development of along-ridge winds that take the form of a barrier jet over the western slope of the mountain range. Such upstream wind disturbances are either weak or nonexistent in a high-Fr case. A critical Fr (Frc) of 0.35 inferred in this study is within the range of those suggested in previous observational and numerical studies. The depth of the blocked layer estimated from the along-ridge wind profile upstream of the northern Sierra Nevada corresponds to Frc between 0.3 and 0.45 as well. Associated with these low-level wind disturbances are significant low-level southerly moisture fluxes over the western slope and foothills of the Sierra Nevada in the low-Fr case, which result in significant exports of moisture from the southern Sierra Nevada to the northern region. This along-ridge low-level water vapor transport by blocking-induced barrier jets in a low-Fr condition may result in a strong north–south precipitation gradient over the Sierra Nevada.

scholarly journals The 13–14 December 2001 IMPROVE-2 Event. Part III: Simulated Microphysical Budgets and Sensitivity Studies

2005 ◽  
Vol 62 (10) ◽  
pp. 3535-3558 ◽  
Author(s):  
Brian A. Colle ◽  
Matthew F. Garvert ◽  
Justin B. Wolfe ◽  
Clifford F. Mass ◽  
Christopher P. Woods
Keyword(s):  
Water Vapor ◽  
Mesoscale Model ◽  
Positive Impact ◽  
Cloud Water ◽  
Precipitation Forecast ◽  
State University ◽  
Microphysical Process ◽  
Surface Precipitation ◽  
Sensitivity Studies ◽  
Microphysical Parameterization

Abstract This paper investigates the microphysical pathways and sensitivities within the Reisner-2 bulk microphysical parameterization (BMP) of the fifth-generation Pennsylvania State University–National Center for Atmospheric Research (PSU–NCAR) Mesoscale Model (MM5) for the Improvement of Microphysical Parameterization through Observational Verification Experiment (IMPROVE)-2 field experiment on 13–14 December 2001. A microphysical budget over the windward slope at 1.33-km horizontal grid spacing was calculated, in which the importance of each microphysical process was quantified relative to the water vapor loss (WVL) rate. Over the windward Cascades, the largest water vapor loss was associated with condensation (73% of WVL) and snow deposition (24%), and the windward surface precipitation resulted primarily from accretion of cloud water by rain (27% of WVL), graupel fallout and melt (19%), and snowmelt (6%). Two-thirds of the snow generated aloft spilled over into the lee in an area of model overprediction, resulting in windward precipitation efficiency of only 50%. Even with the large amount of precipitation spillover, the windward precipitation was still overpredicted in many locations. A series of experiments were completed using different snowfall speeds, cloud water autoconversion, threshold riming values for snow to graupel autoconversion, and slope intercepts for snow. The surface precipitation was most sensitive to those parameters associated with the snow size distribution and fall speed, while decreasing the riming threshold for snow to graupel conversion had the greatest positive impact on the precipitation forecast. All simulations overpredicted cloud water over the lower windward slopes, had too little cloud water over the crest, and had too much ice at moderate-to-large sizes aloft. Riming processes were important, since without supercooled water there were bull’s-eyes of spurious snow spillover over the lee slopes.

scholarly journals On the Potential Change in Surface Water Vapor Deposition over the Continental United States due to Increases in Atmospheric Greenhouse Gases

2006 ◽  
Vol 19 (8) ◽  
pp. 1576-1585
Author(s):  
Zaitao Pan ◽  
Moti Segal ◽  
Charles Graves
Keyword(s):  
United States ◽  
Water Vapor ◽  
Surface Water ◽  
Vapor Deposition ◽  
Climate Model ◽  
Regional Climate ◽  
Climate Scenario ◽  
The United States ◽  
Eastern United States ◽  
Present Climate

Abstract Characteristics of surface water vapor deposition (WVD) over the continental United States under the present climate and a future climate scenario reflecting the mid-twenty-first-century increased greenhouse gas concentrations were evaluated by using a regional climate model forced by initial and lateral boundary conditions generated by a GCM. Simulated seasonal WVD frequency and daily amounts are presented and elaboration on their relation to potential surface dew/frost is also provided. The climate scenario showed in winter a noticeable decline in WVD frequency over snow-covered areas in the Midwest and over most of the elevated terrain in the western United States, contrasted by an overall increase in the eastern United States. In summer, a decline in frequency was simulated for most of the United States, particularly over the mountains in the west. A spatially mixed trend of change in the frequency was indicated in spring and fall. The trend of change in WVD amount resembled that of the frequency in summer, whereas a largely reversed relation was shown in winter. Quantitatively, changes in frequency and amount of WVD in the range of −30% to +30% generally were indicated for all locations and seasons, except for the western half of the United States, where the change was larger in summer. While areas passing a local statistical test on WVD changes ranged from 11% to 36% of land domain, the WVD differences as a whole field between present climate and future scenarios are significant.

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