Dominant modes of winter precipitation variability over Central Southwest Asia and inter-decadal change in the ENSO teleconnection

Rana, Sapna; McGregor, James; Renwick, James

doi:10.1007/s00382-019-04889-9

Cited by 30 publications

(31 citation statements)

References 85 publications

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“…The EA‐WA sector has been previously identified as being a region where precipitation can be forecast with higher skill compared to most places of the globe on the subseasonal time scale (Tippett et al, ; Vigaud et al, ). Enhanced probabilities of above‐normal rainfall in Week 3–4 forecasts (i.e., 15–28 days in advance) for starts during El Niño and MJO Phase 7 are consistent with regional influences from ENSO (Abid et al, ; Alizadeh‐Choobari et al, ; Atif et al, ; Barlow et al, ; Hoell et al, ; Hoell, Barlow, Cannon, & Xu, ; Kang et al, ; Kijazi and Reason, ; Mutai and Ward, ; Nicholson, ; Soltani et al, ; Rana et al, , ) and the MJO (Barlow et al, , ; Hoell et al, ; Hoell, Cannon, & Barlow, ; Mutai and Ward, ; Pohl and Camberlin, , ; Pohl et al, ; Nazemosadat and Ghaedamini, ; Nazemosadat and Shahgholian, ). As noted in the recent review from Barlow et al (), regional droughts have also been related to ENSO (Al Senafi and Anis, ; Athar, ; Barlow et al, ; Donat et al, ; Hoell et al, , , ; Krichak et al, ; Mariotti et al, ; Mariotti, ; Nazemosadat and Ghasemi, ; Niranjan and Ouarda, ; Price et al, ; Syed et al, ; Yin et al, ) and the MJO (Barlow et al, ; Barlow, ; Hoell et al, ; Nazemosadat and Ghaedamini, ; Pourasghar et al, ; Tippett et al, ).…”

Section: Introductionmentioning

confidence: 54%

Deterministic Skill of Subseasonal Precipitation Forecasts for the East Africa‐West Asia Sector from September to May

Vigaud¹,

Tippett

Robertson³

2019

JGR Atmospheres

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The East Africa-West Asia (EA-WA) sector is a region where the skill in forecasting rainfall is unusually high in the subseasonal-to-seasonal (S2S) time range and where ENSO and MJO signals have significant impacts. Much of regional rainfall intra-seasonal variability is related to tropical-temperate interactions on synoptic time scales, and we examine whether the skill of dynamical S2S forecasts for the region exceeds the predictability associated with ENSO and the MJO. Deterministic skill (Spearman's rank correlation) of multimodel ensemble forecasts of weekly and Week 3-4 precipitation averages is examined for starts in September-April, based on three ensemble prediction systems (EPS) from the S2S prediction project over the common 1999-2010 reforecasts period. The skill of weekly forecasts decreases with increasing lead but remains statistically significant out to Week 3 and Week 4, a level of skill that has not been previously reported at such leads. The skill of Week 3-4 forecasts is higher than that of Week 3 or Week 4 forecasts. The prediction skill of weekly and 2-week precipitation averages from ENSO and the MJO is estimated using a multiple linear regression and found to be less than that achieved by the dynamical forecasts for Week 3, Week 4, and Week 3-4 targets. This is evidence for achievable forecast skill that extends beyond typical weather-scale lead times and that is not simply related to ENSO or MJO signals. The opportunity for skillful predictions is illustrated through successful forecasts up to 4 weeks in advance of extreme rainfall over the Arabian peninsula related to strong tropical-temperate interactions during weak ENSO and MJO conditions.

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Section: Introductionmentioning

confidence: 54%

Deterministic Skill of Subseasonal Precipitation Forecasts for the East Africa‐West Asia Sector from September to May

Vigaud¹,

Tippett

Robertson³

2019

JGR Atmospheres

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“…Weakening of the SH encourages disturbances in the weaker subtropical jet, allowing for WWD to propagate toward HMA, increasing precipitation in Central Himalayas (Cohen and Entekhabi, 1999;Wu and Wang, 2002;Cannon et al, 2015). Rana et al (2019) shows that ridging that extends into central Asia and Europe during SH+ blocks eastward propagating westerly storm system, and restricts westerly flow to more southerly latitudes, resulting in increased precipitation in the southern region of CSWA. Table 1 indicates that Karakoram and Pamir ARs are significantly more frequent during SH-compared to neutral.…”

Section: Climate Modulationmentioning

confidence: 99%

“…During the warm phase of ENSO, when the tropical oceans are warmer than usual, anomalous upper-level convergence over southern Asia has been shown to intensify WWDs (Yadav et al, 2009;Thapa et al, 2018). (Rana et al, 2019) explains that increased precipitation in Central Southwest Asia (CSWA) during winter season El Niño years is mainly attributed to a deepened trough over CSWA with cyclonic circulation that enhances southwesterly flow and moist air advection from the Indian Ocean basin into CSWA. Guan and Waliser (2015) found that El Niño conditions slightly increase NDJFM AR frequency in southwest and southern Asia but has no considerable impact on precipitation.…”

Section: Climate Modulationmentioning

confidence: 99%

Winter And Spring Atmospheric Rivers In High Mountain Asia: Climatology, Dynamics, And Variability

Nash¹,

Carvalho²

2021

Preprint

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Atmospheric Rivers (ARs) that reach the complex terrain of High Mountain Asia (HMA) cause significant hydrological impacts for millions of people. While ARs are often associated with precipitation extremes and can cause floods and debris flows affecting populated communities, little is known about ARs that reach as far inland as HMA. This paper characterizes AR types and investigates dynamical mechanisms associated with the development of ARs that typically affect HMA. Combined empirical orthogonal function (cEOF) analysis using integrated water vapor transport (IVT) is applied to days where an AR reaches HMA. K-means cluster analysis applied to the first two principal components uncovered three subtypes of AR events with distinct synoptic characteristics during winter and spring months. The first subtype increases precipitation and IVT in the Karakoram and is associated with a zonally oriented wave train propagating within the westerly jet waveguide. The second subtype is associated with enhanced southwesterly IVT, anomalous upper-level cyclonic circulation centered on 45°E, and precipitation in the Pamirs. The third subtype shows anomalous precipitation in the Eastern Himalayas and southwesterly IVT across the Bay of Bengal. Interannual variations in the frequency of HMA ARs and relationships with various teleconnection patterns show that western HMA AR subtypes are sensitive to well-known remote large-scale climate factors, such as the El Niño Southern Oscillation, Arctic Oscillation, and the Siberian High. These results provide synoptic characterization of the three types of ARs that reach HMA and reveal the previously unexplored significance of their contribution to winter and spring precipitation.

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“…The average response of precipitation to El Niño and La Niña phases of ENSO is investigated in several studies (Barlow et al ., 2002; Nazemosadat and Ghasemi, 2004; Hoell et al ., 2017a; Alizadeh‐Choobari et al ., 2018). A consistent finding between previous studies is that wet and dry conditions are accompanied respectively by El Niño and La Niña (Nazemosadat and Ghasemi, 2004; Barlow et al ., 2016; Rana et al ., 2017, 2019; Hoell et al ., 2017a, 2017b, 2018; Alizadeh‐Choobari et al ., 2018). The range of response is reported by Hoell et al .…”

Section: Introductionmentioning

confidence: 99%

“…The first leading mode of winter precipitation (EOF‐1) is significantly linked to ENSO characterized by a mono‐sign pattern according to findings by Rana et al . (2019). Simulations based on a large ensemble of atmospheric models (three models, 42 members) forced by 1901–2012 time varying boundary conditions show the association of wet years with El Niño throughout the whole period and exceptionally dry conditions with La Niña after 1970 (Hoell et al ., 2017a).…”

Section: Introductionmentioning

confidence: 99%

Improved multi‐model ensemble forecasts of Iran's precipitation and temperature using a hybrid dynamical‐statistical approach during fall and winter seasons

Najafi

Robertson

Bavani

et al. 2021

Intl Journal of Climatology

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Skillful seasonal climate forecasts can support decision making in water resources management and agricultural planning. In arid and semi‐arid regions, tailoring reliable forecasts has the potential to improve water management by using key hydroclimate variables months in advance. This article analyses and compares the performance of two common approaches (empirical and hybrid dynamical‐statistical) in seasonal climate forecasting over a drought‐prone area located in Southwest Asia including Iran. Empirical models are framed as a baseline skill that hybrid models need to outperform. Both approaches provide probabilistic forecasts of precipitation and temperature using canonical correlation analysis to provide forecasts at 0.25° resolution. Empirical models are developed based on the large‐scale observed atmosphere–ocean patterns for forecasting using antecedent climate anomalies as predictors, while the hybrid approach makes use of model output statistics to correct systematic errors in dynamical climate model forecast outputs. Eight state‐of‐the‐art dynamical models from the North American Multi‐Model Ensemble project are analysed. Individual models with the highest goodness index are weighted to develop seven different hybrid dynamical‐statistical Multi‐model Ensembles. In this study, (October–December) and (January–February) are considered as target seasons which are the most important periods within the water year for water resource allocation to the agriculture sector. The results show that the hybrid approach has improved performance compared to the raw general circulation models and purely empirical models, and that the performance of the hybrid models is season‐dependent. Seasonal forecasts of precipitation (temperature) have a higher skill in OND (JFM). In addition, in most cases, Multi‐model Ensemble (MME) is more skillful than the empirical models and outperforms individual dynamical models. However, the best individual model might be as skillful as the MME given the target season and region of interest.

show abstract

Dominant modes of winter precipitation variability over Central Southwest Asia and inter-decadal change in the ENSO teleconnection

Cited by 30 publications

References 85 publications

Deterministic Skill of Subseasonal Precipitation Forecasts for the East Africa‐West Asia Sector from September to May

Deterministic Skill of Subseasonal Precipitation Forecasts for the East Africa‐West Asia Sector from September to May

Winter And Spring Atmospheric Rivers In High Mountain Asia: Climatology, Dynamics, And Variability

Improved multi‐model ensemble forecasts of Iran's precipitation and temperature using a hybrid dynamical‐statistical approach during fall and winter seasons

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