Spring and Summer 1988 Drought over the Contiguous United States—Causes and Prediction

Namias, Jerome

doi:10.1175/1520-0442(1991)004<0054:sasdot>2.0.co;2

Cited by 155 publications

(86 citation statements)

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“…Earlier studies did not suggest strong relationships between the NAM and ENSO (Namias, 1991;Adams and Comrie, 1997), however the continental-scale anomalous anticyclone prevailing in summer over North America during La Niña and contrasting with weaker impacts during El Niño (Wang et al, 2007) might be of relevance to the NAM. Over West Africa, Sahelian rainfall relationships to ENSO have only been evidenced since the 1990s (Semazzi et al, 1988;Rowell et al, 1992;Janicot et al, 1996), El Niño (La Niña) being associated with dry (wet) conditions over the Sahel.…”

Section: Introductionmentioning

confidence: 79%

Subseasonal Predictability of Boreal Summer Monsoon Rainfall from Ensemble Forecasts

Vigaud

Robertson

Tippett

et al. 2017

Front. Environ. Sci.

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Subseasonal forecast skill over the broadly defined North American (NAM), West African (WAM) and Asian (AM) summer monsoon regions is investigated using three Ensemble Prediction Systems (EPS) at sub-monthly lead times. Extended Logistic Regression (ELR) is used to produce probabilistic forecasts of weekly and week 3-4 averages of precipitation with starts in May-Aug, over the 1999-2010 period. The ELR tercile category probabilities for each model gridpoint are then averaged together with equal weight. The resulting Multi-Model Ensemble (MME) forecasts exhibit good reliability, but have generally low sharpness for forecasts beyond 1 week; Multi-model ensembling largely removes negative values of the Ranked Probability Skill Score (RPSS) seen in individual forecasts, and broadly improves the skill obtained in any of the three individual models except for the AM. The MME week 3-4 forecasts have generally higher RPSS and comparable reliability over all monsoon regions, compared to week 3 or week 4 forecast separately. Skill is higher during La Niña compared to El Niño and ENSO-neutral conditions over the 1999-2010 period, especially for the NAM. Regionally averaged RPSS is significantly correlated with the Maden-Julian Oscillation (MJO) for the AM and WAM. Our results indicate potential for skillful predictions at subseasonal time-scales over the three summer monsoon regions of the Northern Hemisphere.

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Section: Introductionmentioning

confidence: 79%

Subseasonal Predictability of Boreal Summer Monsoon Rainfall from Ensemble Forecasts

Vigaud

Robertson

Tippett

et al. 2017

Front. Environ. Sci.

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“…Storms transform carbon stocks from living biomass to dead wood and thus increase the risk of fire and pathogen outbreaks (Negrón-Juárez and Chambers, 2010). Droughts and heat waves have an impact on plant physiology, phenology and carbon allocation Reichstein et al, 2007;Phillips et al, 2009).…”

Section: Introductionmentioning

confidence: 99%

Extreme events in gross primary production: a characterization across continents

et al. 2014

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Abstract. Climate extremes can affect the functioning of terrestrial ecosystems, for instance via a reduction of the photosynthetic capacity or alterations of respiratory processes. Yet the dominant regional and seasonal effects of hydrometeorological extremes are still not well documented and in the focus of this paper. Specifically, we quantify and characterize the role of large spatiotemporal extreme events in gross primary production (GPP) as triggers of continental anomalies. We also investigate seasonal dynamics of extreme impacts on continental GPP anomalies. We find that the 50 largest positive extremes (i.e., statistically unusual increases in carbon uptake rates) and negative extremes (i.e., statistically unusual decreases in carbon uptake rates) on each continent can explain most of the continental variation in GPP, which is in line with previous results obtained at the global scale. We show that negative extremes are larger than positive ones and demonstrate that this asymmetry is particularly strong in South America and Europe. Our analysis indicates that the overall impacts and the spatial extents of GPP extremes are power-law distributed with exponents that vary little across continents. Moreover, we show that on all continents and for all data sets the spatial extents play a more important role for the overall impact of GPP extremes compared to the durations or maximal GPP. An analysis of possible causes across continents indicates that most negative extremes in GPP can be attributed clearly to water scarcity, whereas extreme temperatures play a secondary role. However, for Europe, South America and Oceania we also identify fire as an important driver. Our findings are consistent with remote sensing products. An independent validation against a literature survey on specific extreme events supports our results to a large extent.

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“…The study builds on the results of a number of earlier studies that found that summertime Rossby waves have played an important role in summer climate extremes. For example, Namias (1983;1991) found that warns season droughts over the US Great Plains (e.g, the 1988 drought) tend to be associated with upper level anticyclones linked to standing Rossby wave patterns. Lyon and Dole (1995) showed that both the 1980 and 1988 droughts were associated with anomalous stationary wave patterns, with apparent source regions in the North Pacific.…”

Section: Introductionmentioning

confidence: 99%

Warm Season Subseasonal Variability and Climate Extremes in the Northern Hemisphere: The Role of Stationary Rossby Waves

2011

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This study examines the nature of boreal summer subseasonal atmospheric variability based on the new NASA Modern-Era Retrospective analysis for Research and Applications (MERRA) for the period 1979-2010. An analysis of the June, July and August subseasonal 250hPa v-wind anomalies shows distinct Rossby wave-like structures that appear to be guided by the mean jets.On monthly subseasonal time scales, the leading waves (the first 10 rotated empirical orthogonal functions or REOFs of the 250hPa v-wind) explain about 50% of the Northern Hemisphere vwind variability, and account for more than 30% (60%) of the precipitation (surface temperature) variability over a number of regions of the northern middle and high latitudes, including the U.S.northern Great Plains, parts of Canada, Europe, and Russia. The first REOF in particular, consists of a Rossby wave that extends across northern Eurasia where it is a dominant contributor to monthly surface temperature and precipitation variability, and played an important role in the 2003 European and 2010 Russian heat waves. While primarily subseasonal in nature, the Rossby waves can at times have a substantial seasonal mean component. This is exemplified by REOF 4 which played a major role in the development of the most intense anomalies of the U.S. 1988 drought (during June) and the 1993 flooding (during July), though differed in the latter event by also making an important contribution to the seasonal mean anomalies. A stationary wave model (SWM) is used to reproduce some of the basic features of the observed waves and provide insight into the nature of the forcing. In particular, the responses to a set of idealized forcing functions are used to map the optimal forcing patterns of the leading waves. Also, experiments to reproduce the observed waves with the SWM using MERRA-based estimates of the forcing indicate that the wave forcing is dominated by sub-monthly vorticity transients.

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Spring and Summer 1988 Drought over the Contiguous United States—Causes and Prediction

Cited by 155 publications

References 0 publications

Subseasonal Predictability of Boreal Summer Monsoon Rainfall from Ensemble Forecasts

Subseasonal Predictability of Boreal Summer Monsoon Rainfall from Ensemble Forecasts

Extreme events in gross primary production: a characterization across continents

Warm Season Subseasonal Variability and Climate Extremes in the Northern Hemisphere: The Role of Stationary Rossby Waves

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