Soil Moisture and the Persistence of North American Drought

Oglesby, Robert J.; Erickson, D. J.

doi:10.1175/1520-0442(1989)002<1362:smatpo>2.0.co;2

Cited by 201 publications

(119 citation statements)

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“…The SMOIS-induced surface pressure drop is consistent with the decrease in the 850 hPa geopotential heights. In previous soil moisture sensitivity experiments over North America using various climate models, Oglesby and Erickson (1989) and Pal and Eltahir (2003) found heat lows at the surface and enhanced positive height anomalies in the upper atmosphere because of reduced soil moisture. Fischer et al (2007) conducted sensitivity experiments for the 2003 European heatwave and found a weak surface heat low and enhanced ridging in the mid-troposphere due to reduced soil moisture; they suggested that a positive feedback mechanism exists between soil moisture, continental-scale circulation and temperature.…”

Section: Atmospheric Circulationmentioning

confidence: 90%

Sensitivity of high-temperature weather to initial soil moisture: a case study using the WRF model

et al. 2014

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Abstract. Using a succession of 24 h Weather Research andForecasting model (WRF) simulations, we investigate the sensitivity to initial soil moisture of a short-range hightemperature weather event that occurred in late July 2003 in East China. The initial soil moisture (SMOIS) in the Noah land surface scheme is adjusted (relative to the control run, CTL) for four groups of simulations: DRY25 (−25 %), DRY50 (−50 %), WET25 (+25 %) and WET50 (+50 %). Ten 24 h integrations are performed in each group.We focus on 2 m surface air temperature (SAT) greater than 35 • C (the threshold of "high-temperature" events in China) at 06:00 UTC (roughly 14:00 LT in the study domain) to analyse the occurrence of the high-temperature event. The 10-day mean results show that the 06:00 UTC SAT (SAT06) is sensitive to the SMOIS change; specifically, SAT06 exhibits an apparent increase with the SMOIS decrease (e.g. compared with CTL, DRY25 generally results in a 1 • C SAT06 increase over the land surface of East China), areas with 35 • C or higher SAT06 are the most affected, and the simulations are more sensitive to the SMOIS decrease than to the SMOIS increase, which suggests that hot weather can be amplified under low soil moisture conditions. Regarding the mechanism underlying the extremely high SAT06, sensible heat flux has been shown to directly heat the lower atmosphere, and latent heat flux has been found to be more sensitive to the SMOIS change, resulting in an overall increase in surface net radiation due to the increased greenhouse effect (e.g. with the SMOIS increase from DRY25 to CTL, the 10-day mean net radiation increases by 5 W m −2 ). Additionally, due to the unique and dynamic nature of the western Pacific subtropical high, negative feedback occurs between the regional atmospheric circulation and the air temperature in the lower atmosphere while positive feedback occurs in the midtroposphere.Using a method based on an analogous temperature relationship, a detailed analysis of the physical processes shows that for the SAT change, the SMOIS change affects diabatic processes (e.g. surface fluxes) more strongly than the adiabatic process of subsidence in the western Pacific subtropical high in the five groups of simulations. Interestingly, although diabatic processes dominate subsidence during the daytime and night-time separately, they do not necessarily dominate during the 24 h periods (e.g. they are dominant in the WET and CTL simulations only). Further, as the SMOIS decreases, the SAT06 increases, which is largely due to the reduced cooling effect of the diabatic processes, rather than the warming effect of subsidence.Unlike previous studies on heatwave events at climate timescales, this paper presents the sensitivity of simulated short-term hot weather to initial soil moisture and emphasises the importance of appropriate soil moisture initialization when simulating hot weather.

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Section: Atmospheric Circulationmentioning

confidence: 90%

Sensitivity of high-temperature weather to initial soil moisture: a case study using the WRF model

et al. 2014

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“…Additionally, the role of land surface interactions and feedbacks with the regional atmospheric circulation (e.g. Oglesby and Erickson 1989;Oglesby et al 2001) must also be included to fully understand and hence lead to better prediction of prolonged North American droughts. …”

Section: Discussionmentioning

confidence: 99%

Influence of Atlantic sea surface temperatures on persistent drought in North America

2010

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This study investigates the relationship between North Atlantic sea surface temperatures (SST) and persistent drought in North America using modern observations, proxy paleodata, and simulations from multiple climate models. The observational results show that persistent droughts in the Great Plains and the southwest North America are closely related to multidecadal variations of North Atlantic SST (Atlantic Multidecadal Oscillations, AMO). During the AMO warm (cold) phases, most of North America is dry (wet). This relationship is persistent since at least 1567 AD, as based on proxy SST for the North Atlantic and the reconstructed drought index for North America. On centennial timescales, proxy SST records from the North Atlantic and proxy drought records for North America suggest that major periods of AMO-like warm (cold) SST anomalies during the last 7.0 ka correspond to dry (wet) conditions in the Great Plains. The influence of North Atlantic SST on North American droughts is examined using simulations made by five global climate models. When forced by warm North Atlantic SST anomalies, all models captured significant drying over North America, despite some regional differences. Specifically, dry summers in the Great Plains and the southwest North America are simulated by all models. The precipitation response to a cold North Atlantic is much weaker and contains greater disagreement among the models. Overall, the ensemble of the five models could well reproduce the statistical relationship between the dry/wet fluctuations in the North America and North Atlantic SST anomalies. Our results suggest that North Atlantic SSTs are likely a major driver of decadal and centennial timescale circulation, including droughts, in North America. Possible mechanisms that connect North Atlantic SST with North American drought, as well as interactions between North Atlantic and tropical Pacific SST and their relative roles on drought are also discussed.

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“…9e-h). Regions strongly influenced by the advection of Gulf of Mexico moisture show an increase in the advection of this moisture as a result of reduced soil moisture (Oglesby and Erickson 1989). Moisture transport is affected by these changes in LLJ orientation and intensity.…”

Section: Large-scale Atmospheric Processes and Soil Moisture Deficmentioning

confidence: 99%

A Growing-Season Hydroclimatology, Focusing on Soil Moisture Deficits, for the Ohio Valley Region

Grundstein

Bentley

2001

J. Hydrometeor

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A hydroclimatology, or description of long-term means and interannual variation, that focuses on soil moisture deficits was constructed for the period of 1895-1998 for a six-state region composing the Ohio Valley. The term ''deficit'' is considered from an agricultural point of view whereby moisture-induced crop stress is a combination of insufficient precipitation and soil moisture. Of particular concern are deficits that occur during the growing season (May-September) when vegetation is most susceptible to moisture-induced stress. Evidence suggests that there is considerable temporal variability but no long-term trend toward either wetter or drier conditions in the Ohio Valley. The pattern of growing-season deficit is characterized by multiyear and multidecadal cycles of wet and dry periods. Decreases in precipitation during years with anomalously large growing-season deficits, however, are associated more with the reduced frequency of precipitation events than with any changes in intensity. These variations in precipitation frequency and the conditions conducive to droughts are intimately linked with largescale atmospheric conditions, including the low-level and upper-level flow patterns.

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Soil Moisture and the Persistence of North American Drought

Cited by 201 publications

References 0 publications

Sensitivity of high-temperature weather to initial soil moisture: a case study using the WRF model

Sensitivity of high-temperature weather to initial soil moisture: a case study using the WRF model

Influence of Atlantic sea surface temperatures on persistent drought in North America

A Growing-Season Hydroclimatology, Focusing on Soil Moisture Deficits, for the Ohio Valley Region

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