Variability of the cold season climate in central asia. Part II: Hydroclimatic predictability

• Published in: Journal of Climate
• Main Authors: Gerlitz, Lars, Steirou, Eva, Schneider, Christoph, Moron, Vincent, Vorogushyn, Sergiy, Merz, Bruno
• Other Authors: Hydrology Section, German Research Centre for Geosciences - Helmholtz-Centre Potsdam (GFZ), Humboldt University Of Berlin, Centre européen de recherche et d'enseignement des géosciences de l'environnement (CEREGE), Institut de Recherche pour le Développement (IRD)-Institut National de la Recherche Agronomique (INRA)-Aix Marseille Université (AMU)-Collège de France (CdF (institution))-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), University of Potsdam = Universität Potsdam
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2019
• Subjects: asia; seasonal forecasting; north atlantic oscillation; southern oscillation; climate prediction; [SDV]Life Sciences [q-bio]; [SDU]Sciences of the Universe [physics]; Arctic; North Atlantic; North Atlantic oscillation
• Online Access: https://hal.inrae.fr/hal-02618895; https://hal.inrae.fr/hal-02618895/document; https://hal.inrae.fr/hal-02618895/file/%5B15200442%20-%20Journal%20of%20Climate%5D%20Variability%20of%20the%20Cold%20Season%20Climate%20in%20Central%20Asia.%20Part%20II%20Hydroclimatic%20Predictability.pdf; https://doi.org/10.1175/JCLI-D-18-0892.1

International audience Central Asia (CA) is subjected to a large variability of precipitation. This study presents a statistical model, relating precipitation anomalies in three subregions of CA in the cold season (November-March) with various predictors in the preceding October. Promising forecast skill is achieved for two subregions covering 1) Uzbekistan, Turkmenistan, Kyrgyzstan, Tajikistan, and southern Kazakhstan and 2) Iran, Afghanistan, and Pakistan. ENSO in October is identified as the major predictor. Eurasian snow cover and the quasi-biennial oscillation further improve the forecast performance. To understand the physical mechanisms, an analysis of teleconnections between these predictors and the wintertime circulation over CA is conducted. The correlation analysis of predictors and large-scale circulation indices suggests a seasonal persistence of tropical circulation modes and a dynamical forcing of the westerly circulation by snow cover variations over Eurasia. An EOF analysis of pressure and humidity patterns allows separating the circulation variability over CA into westerly and tropical modes and confirms that the identified predictors affect the respective circulation characteristics. Based on the previously established weather type classification for CA, the predictors are investigated with regard to their effect on the regional circulation. The results suggest a modification of the Hadley cell due to ENSO variations, with enhanced moisture supply from the Arabian Gulf during El Nino. They further indicate an influence of Eurasian snow cover on the wintertime Arctic Oscillation (AO) and Northern Hemispheric Rossby wave tracks. Positive anomalies favor weather types associated with dry conditions, while negative anomalies promote the formation of a quasi-stationary trough over CA, which typically occurs during positive AO conditions.