scholarly journals Attribution of the Seasonality and Regionality in Climate Trends over the United States during 1950–2000

2009 ◽  
Vol 22 (10) ◽  
pp. 2571-2590 ◽  
Author(s):  
Hailan Wang ◽  
Siegfried Schubert ◽  
Max Suarez ◽  
Junye Chen ◽  
Martin Hoerling ◽  
...  
Keyword(s):  
United States ◽  
General Circulation ◽  
Decadal Variability ◽  
Circulation Model ◽  
Late Summer ◽  
The United States ◽  
Phase Changes ◽  
Climate Trends ◽  
Sst Variability ◽  
Central United States

Abstract The observed climate trends over the United States during 1950–2000 exhibit distinct seasonality and regionality. The surface air temperature exhibits a warming trend during winter, spring, and early summer and a modest countrywide cooling trend in late summer and fall, with the strongest warming occurring over the northern United States in spring. Precipitation trends are positive in all seasons, with the largest trend occurring over the central and southern United States in fall. This study investigates the causes of the seasonality and regionality of those trends, with a focus on the cooling and wetting trends in the central United States during late summer and fall. In particular, the authors examine the link between the seasonality and regionality of the climate trends over the United States and the leading patterns of sea surface temperature (SST) variability, including a global warming (GW) pattern and a Pacific decadal variability (PDV) pattern. A series of idealized atmospheric general circulation model (AGCM) experiments were performed forced by SST trends associated with these leading SST patterns, as well as the residual trend pattern (obtained by removing the GW and PDV contributions). The results show that the observed seasonal and spatial variations of the climate trends over the United States are to a large extent explained by changes in SST. Among the leading patterns of SST variability, the PDV pattern plays a prominent role in producing both the seasonality and regionality of the climate trends over the United States. In particular, it is the main contributor to the apparent cooling and wetting trends over the central United States. The residual SST trend, a manifestation of phase changes of the Atlantic multidecadal SST variation during 1950–2000, also exerts influences that show strong seasonality with important contributions to the central U.S. temperature and precipitation during the summer and fall seasons. In contrast, the response over the United States to the GW SST pattern is an overall warming with little seasonality or regional variation. These results highlight the important contributions of decadal and multidecadal variability in the Pacific and Atlantic in explaining the observed seasonality and regionality of the climate trends over the United States during the period of 1950–2000.

Multimodel Estimates of Atmospheric Response to Modes of SST Variability and Implications for Droughts

2010 ◽  
Vol 23 (16) ◽  
pp. 4327-4341 ◽  
Author(s):  
Philip J. Pegion ◽  
Arun Kumar
Keyword(s):  
United States ◽  
Climate Variability ◽  
General Circulation ◽  
Dominant Role ◽  
Circulation Model ◽  
The United States ◽  
Precipitation Variability ◽  
Climate Extreme ◽  
Central Pacific ◽  
Sst Variability

Abstract A set of idealized global model experiments was performed by several modeling centers as part of the Drought Working Group of the U.S. Climate Variability and Predictability component of the World Climate Research Programme (CLIVAR). The purpose of the experiments was to assess the role of the leading modes of sea surface temperature (SST) variability on the climate over the continents, with particular emphasis on the influence of SSTs on surface climate variability and droughts over the United States. An analysis based on several models gives more creditability to the results since it relies on the assessment of impacts that are robust across different models. Coordinated atmospheric general circulation model (AGCM) simulations forced with three modes of SST variability were analyzed. The results show that the SST-forced precipitation variability over the central United States is dominated by the SST mode with maximum loading in the central Pacific Ocean. The SST mode with loading in the Atlantic Ocean, and a mode that is dominated by trends in SSTs, lead to a smaller response. Based on the response to the idealized SSTs, the precipitation response for the twentieth century was also reconstructed. A comparison with the Atmospheric Model Intercomparison Project (AMIP) simulations forced with the observed SSTs illustrates that the reconstructed precipitation variability was similar to the one in the AMIP simulations, further supporting the conclusion that the SST modes identified in the present analysis play a dominant role in the precipitation variability over the United States. One notable exception is the Dust Bowl of the 1930s, and further analysis regarding this major climate extreme is discussed.

Simulated U.S. Drought Response to Interannual and Decadal Pacific SST Variability

2015 ◽  
Vol 28 (12) ◽  
pp. 4688-4705 ◽  
Author(s):  
Robert J. Burgman ◽  
Youkyoung Jang
Keyword(s):  
United States ◽  
Great Plains ◽  
General Circulation ◽  
Decadal Variability ◽  
Low Frequency ◽  
Circulation Model ◽  
Relative Amplitude ◽  
Drought Response ◽  
Sst Variability ◽  
Sst Forcing

Abstract Idealized atmospheric general circulation model (AGCM) experiments by the U.S. Climate Variability and Predictability Program (CLIVAR) Drought Working Group were used in order to study the influence of natural modes of sea surface temperature (SST) variability in the Pacific on drought in the contiguous United States. The current study expands on previous results by examining the atmospheric response of three AGCMs to three different patterns of the idealized Pacific SST anomalies that operate on different time scales: low-frequency (decadal), high-frequency (interannual), and a pan-Pacific pattern that retains characteristics of interannual and decadal variability. While forcing patterns are generally similar in appearance, results indicate that differences in the relative amplitude of the equatorial and extratropical components of the SST forcing are sufficient to give rise to differing teleconnections, leading to regional differences in the amplitude and significance of the precipitation response. Results indicate that the differences in simulated drought response between AGCMs to different cool-phase (La Niña–like) SST patterns are determined by model sensitivity to changes in the relative amplitude of the equatorial and extratropical components of the SSTA forcing, the strength of the land–atmosphere coupling, and by the amplitude of internal atmospheric variability. Results indicate that the northwestern United States and Great Plains regions are particularly sensitive to the extratropical component of the SST forcing. Evidence is also found that when the cool-phase patterns of SST combine, as they have in recent years, constructive interference leads to an enhanced drought response over the Great Plains.

scholarly journals Baseline Conditions and Projected Future Hydro-Climatic Change in National Parks in the Conterminous United States

Water ◽  
2020 ◽  
Vol 12 (6) ◽  
pp. 1704
Author(s):  
William Battaglin ◽  
Lauren Hay ◽  
David Lawrence ◽  
Greg McCabe ◽  
Parker Norton
Keyword(s):  
United States ◽  
Climatic Change ◽  
National Park ◽  
General Circulation ◽  
Circulation Model ◽  
The United States ◽  
Climatic Conditions ◽  
Balance Model ◽  
Climate Simulations ◽  
Baseline Conditions

The National Park Service (NPS) manages hundreds of parks in the United States, and many contain important aquatic ecosystems and/or threatened and endangered aquatic species vulnerable to hydro-climatic change. More effective management of park resources under future hydro-climatic uncertainty requires information on both baseline conditions and the range of projected future conditions. A monthly water balance model was used to assess baseline (1981–1999) conditions and a range of projected future hydro-climatic conditions in 374 NPS parks. General circulation model outputs representing 214 future climate simulations were used to drive the model. Projected future changes in air temperature (T), precipitation (p), and runoff (R) are expressed as departures from historical baselines. Climate simulations indicate increasing T by 2030 for all parks with 50th percentile simulations projecting increases of 1.67 °C or more in 50% of parks. Departures in 2030 p indicate a mix of mostly increases and some decreases, with 50th percentile simulations projecting increases in p in more than 70% of parks. Departures in R for 2030 are mostly decreases, with the 50th percentile simulations projecting decreases in R in more than 50% of parks in all seasons except winter. Hence, in many NPS parks, R is projected to decrease even when p is projected to increase because of increasing T in all parks. Projected changes in future hydro-climatic conditions can also be assessed for individual parks, and Rocky Mountain National Park and Congaree National Park are used as examples.

The Precipitation Response over the Continental United States to Cold Tropical Pacific Sea Surface Temperatures

2014 ◽  
Vol 27 (13) ◽  
pp. 5036-5055 ◽  
Author(s):  
Hailan Wang ◽  
Siegfried Schubert
Keyword(s):  
United States ◽  
Warm Season ◽  
The United States ◽  
Tropical Pacific ◽  
Eastern United States ◽  
North Atlantic Subtropical High ◽  
Sst Variability ◽  
The Pacific ◽  
Central United States ◽  
Atmospheric Circulation Anomalies

The dominant pattern of SST variability in the Pacific during its cold phase produces pronounced precipitation deficits over the continental United States throughout the annual cycle. This study investigates the observed physical and dynamical processes through which the cold Pacific pattern affects U.S. precipitation, particularly the causes for the peak dry impacts in fall, as well as the nature of the differences between the summer and fall responses. Results show that the peak precipitation deficit over the United States during fall is primarily due to reduced atmospheric moisture transport from the Gulf of Mexico into the central and eastern United States and secondarily a reduction in local evaporation from land–atmosphere feedback. The former is associated with a strong and systematic low-level northeasterly flow anomaly over the southeastern United States that counteracts the northwest branch of the climatological North Atlantic subtropical high. The above northeasterly anomaly is maintained by both diabatic heating anomalies in the nearby intra-American seas and diabatic cooling anomalies in the tropical Pacific. In contrast, the modest summertime precipitation deficit over the central United States is mainly an intensification of the local dry anomaly in the preceding spring from local land–atmosphere feedback; the rather weak and disorganized atmospheric circulation anomalies over and to the south of the United States make little contribution. An evaluation of the NASA Seasonal-to-Interannual Prediction Project (NSIPP-1) AGCM simulations shows it to be deficient in simulating the warm season tropical convection responses over the intra-American seas to the cold Pacific pattern and thereby the precipitation responses over the United States, a problem that appears to be common to many AGCMs.

scholarly journals Probabilistic Projections of Climate Change for the Mid-Atlantic Region of the United States: Validation of Precipitation Downscaling during the Historical Era*

2012 ◽  
Vol 25 (2) ◽  
pp. 509-526 ◽  
Author(s):  
Liang Ning ◽  
Michael E. Mann ◽  
Robert Crane ◽  
Thorsten Wagener
Keyword(s):  
United States ◽  
General Circulation ◽  
Large Scale ◽  
Daily Precipitation ◽  
Circulation Model ◽  
The United States ◽  
Monthly Precipitation ◽  
Atlantic Region ◽  
Daily Precipitation Data ◽  
Training Interval

Abstract This study uses a statistical downscaling method based on self-organizing maps (SOMs) to produce high-resolution, downscaled precipitation estimates over the state of Pennsylvania in the mid-Atlantic region of the United States. The SOMs approach derives a transfer function between large-scale mean atmospheric states and local meteorological variables (daily point precipitation values) of interest. First, the SOM was trained using seven coarsely resolved atmospheric variables from the National Centers for Environmental Prediction (NCEP) reanalysis dataset to model observed daily precipitation data from 17 stations across Pennsylvania for the period 1979–2005. Employing the same coarsely resolved variables from nine general circulation model (GCM) simulations taken from the historical analysis of the Coupled Model Intercomparison Project, phase 3 (CMIP3), the trained SOM was subsequently applied to simulate daily precipitation at the same 17 sites for the period 1961–2000. The SOM analysis indicates that the nine model simulations exhibit similar synoptic-scale features to the (NCEP) observations over the 1979–2007 training interval. An analysis of the sea level pressure signatures and the precipitation distribution corresponding to the trained SOM shows that it is effective in differentiating characteristic synoptic circulation patterns and associated precipitation. The downscaling approach provides a faithful reproduction of the observed probability distributions and temporal characteristics of precipitation on both daily and monthly time scales. The downscaled precipitation field shows significant improvement over the raw GCM precipitation fields with regard to observed average monthly precipitation amounts, average monthly number of rainy days, and standard deviations of monthly precipitation amounts, although certain caveats are noted.

scholarly journals Characteristics of Drought and Persistent Wet Spells over the United States in the Atmosphere–Land–Ocean Coupled Model Experiments

2012 ◽  
Vol 16 (9) ◽  
pp. 1-26 ◽  
Author(s):  
Kingtse C. Mo ◽  
Lindsey N. Long ◽  
Jae-Kyung E. Schemm
Keyword(s):  
United States ◽  
Extreme Events ◽  
General Circulation ◽  
Coupled Model ◽  
Circulation Model ◽  
The United States ◽  
Agricultural Drought ◽  
The West ◽  
East West ◽  
Wet Spells

Abstract Atmosphere–land–ocean coupled model simulations are examined to diagnose the ability of models to simulate drought and persistent wet spells over the United States. A total of seven models are selected for this study. They are three versions of the NCEP Climate Forecast System (CFS) coupled general circulation model (CGCM) with a T382, T126, and T62 horizontal resolution; GFDL Climate Model version 2.0 (CM2.0); GFDL CM2.1; Max Planck Institute (MPI) ECHAM5; and third climate configuration of the Met Office Unified Model (HadCM3) simulations from the World Climate Research Programme (WCRP) Coupled Model Intercomparison Project phase 3 (CMIP3) experiments. Over the United States, drought and persistent wet spells are more likely to occur over the western interior region, while extreme events are less likely to persist over the eastern United States and the West Coast. For meteorological drought, which is defined by precipitation (P) deficit, the east–west contrast is well simulated by the CFS T382 and the T126 models. The HadCM3 captures the pattern but not the magnitudes of the frequency of occurrence of persistent extreme events. For agricultural drought, which is defined by soil moisture (SM) deficit, the CFS T382, CFS T126, MPI ECHAM5, and HadCM3 models capture the east–west contrast. The models that capture the west–east contrast also have a realistic P climatology and seasonal cycle. ENSO is the dominant mode that modulates P over the United States. A model needs to have the ENSO mode and capture the mean P responses to ENSO in order to simulate realistic drought. To simulate realistic agricultural drought, the model needs to capture the persistence of SM anomalies over the western region.

scholarly journals Climatic Role of North American Low-Level Jets on U.S. Regional Tornado Activity

2012 ◽  
Vol 25 (19) ◽  
pp. 6666-6683 ◽  
Author(s):  
Scott J. Weaver ◽  
Stephen Baxter ◽  
Arun Kumar
Keyword(s):  
United States ◽  
Great Plains ◽  
North American ◽  
Decadal Variability ◽  
Principal Component ◽  
The United States ◽  
Northern Great Plains ◽  
Low Level ◽  
Sst Variability ◽  
Trend Pattern

Abstract Variability of springtime tornadic activity over the United States is assessed through the connectivity of preferred modes of North American low-level jet (NALLJ) variability to the local thermodynamic environment and remote SST variations. The link between regional tornado activity and NALLJ variability as diagnosed from a consistent reanalysis system (i.e., NCEP–NCAR) serves as dynamical corroboration in light of the inhomogeneous tornado database. The analysis reveals a multidecadal variation in the strength of the NALLJ–tornado connection, highlighted by tornado activity in the southern Great Plains region nearly doubling its correlation with NALLJ principal component 1 (PC 1) in recent decades. Locally, this is a result of a southward shift of NALLJ variability modes during the recent period. Motivated by these epochal shifts in NALLJ activity, a comparison of the early (1950–78) and late (1979–2010) tornado and NALLJ SST linkages indicates an Atlantic decadal SST variability influence during the early epoch, with Pacific decadal variability thereafter, highlighting the remote SST influence on the shifts in geographic placement and strength of NALLJ variability. The remote SST variability linkages further reveal that the observed global-scale SST trend pattern over the last 61 years may be contributing to a shift toward weaker tornadoes during spring in the northern Great Plains region. Tornado activity over the southeast region of the United States shows no such relationship to the SST trend pattern during spring, an immunity that is unexpected if spurious trends in the tornado database were influencing the SST linkage.

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