Abstract In early 2018, Cape Town (population ~3.7 million) was at risk of being one the first major metropolitan areas in world to run out water. This due a severe multi-year drought that led levels supply dams falling an unprecedented low. Here we analyze rainfall data from city catchment areas, including rare centennial records surrounding region, assess severity 2015–2017 drought. We find there has been long-term decline number winter days, but this trend generally masked by fluctuations...

Abstract The occurrence of boreal winter Rossby wave breaking (RWB) along with the quantitative role synoptic transient eddy momentum and heat fluxes directly associated RWB are examined during development Euro-Atlantic circulation regimes using ERA-Interim. Results compared to those from seasonal reforecasts made Integrated Forecast System model ECWMF coupled NEMO ocean model. both Scandinavian blocking Atlantic ridge is coincident anticyclonic (AWB); however, do not contribute (and, in...

Abstract A three-dimensional evolution of Madden–Julian oscillation (MJO) diabatic heating for October–March from satellite data is constructed: the propagates eastward three cycles, modulated by likelihood a given MJO phase to occur on calendar day. This added temperature tendencies each member an ensemble 48 (1 October–31 March) simulations with Community Earth System Model. The leading two most predictable modes planetary wave vertically integrated total (added plus model generated)...

Abstract Subtropical anticyclones and midlatitude storm tracks are key components of the large-scale atmospheric circulation. Focusing on Southern Hemisphere, seasonality three dominant subtropical anticyclones, situated over South Pacific, Atlantic, south Indian Ocean basins, has a large influence local weather climate within America, southern Africa, Australia, respectively. Generally speaking, sea level pressure Hemisphere subtropics reaches its seasonal maximum during winter season when...

Bangladesh and northeast India are the most densely populated regions in world where severe floods as a result of extreme rainfall events kill hundreds people cause socio‐economic losses regularly. Owing to local high topography, moisture‐carrying monsoon winds converge near southeast (SEB) (NEBI), which produces significant from May October. Using observed data, we find an increasing trend 1‐day event (150 mmday) frequency during 1950–2021. The quadrupled over western Meghalaya (affecting...

Abstract Atmospheric rivers (ARs) are examined in a set of aquaplanet simulations using the Model for Prediction Across Scales dynamical core run at multiple horizontal resolutions, namely, 240, 120, and 60 km. As resolution is increased, there an increase occurrence long‐lasting ARs. At same time also local finite‐amplitude wave activity (LWA) upper‐tropospheric absolute vorticity, measure Rossby phase amplitude that closely linked with breaking. Consistent notion changes ARs driven by...

Abstract Ensemble reforecast experiments are performed for the boreal winters of 2015/16 (an El Niño year) and 2016/17 in order to understand origin highly unexpected low precipitation over Southern California (SoCal) during 2015/16. The specific hypothesis tested is that December–March anomalies (i) SoCal (highly negative) (ii) 200-hPa height field Pacific–North American (PNA) region (unusual an were forced by tropical diabatic heating, as estimated from reanalysis fields. Ten-member...

Building on the recent advent of concept finite-amplitude wave activity, a contour-following diagnostics for column water vapor (CWV) is developed and applied to pair aquaplanet model simulations understand quantify higher moments in global hydrological cycle. The Lagrangian nature leads more tractable formalism transient, zonally asymmetric component cycle, with strong linear relation emerging between activity precipitation minus evaporation ([Formula: see text]). dry-versus-wet disparity...

Intervention experiments using the Coupled Forecast System model, version 2 (CFSv2), have been performed in which various Madden-Julian Oscillation (MJO) evolutions were added to model’s internally generated heating: Slow Repeated Cycles, Single Cycle, Fast and Cycle. In each experiment, one of these specified MJO tropical diabatic heating was multiple ensemble reforecasts boreal winter (1 November 31 March for winters: 1980–2010). Since re-forecasts made with identical evolution added,...

Abstract Various multivariate statistical methods exist for analyzing covariance and isolating linear relationships between datasets. The most popular are based on singular value decomposition (SVD) include canonical correlation analysis (CCA), maximum (MCA), redundancy (RDA). In this study, continuum power CCA (CPCCA) is introduced as one extension of regression pairs coupled patterns whose temporal variation maximizes the squared partially whitened variables. Similar to whitening...

Abstract Recent studies suggest springtime wet extremes and summertime dry will occur more frequently in the U.S. Midwest, potentially leading to devastating agricultural consequences. To understand role of circulation patterns projected changes seasonal precipitation extremes, k -means clustering approach is applied large-ensemble experiments Community Earth System Model, version 2 (CESM2-LE), ensemble projections CMIP6. We identify two key atmospheric that are associated with extremely...

Abstract In a recent study, Saha et al. (2019, https://doi.org/10.1029/2018JD030082 ) examine the correlation between boreal summer seasonal mean rainfall over India and variance as function of subseasonal time scale find that has local maximum (exceeding value 0.6) for synoptic scales (2–5 day periods). They claim these results to be major advancement in understanding monsoon predictability but do not provide clear physical explanation. Here we sensitivity this relationship details analysis...

Abstract Tropical cyclone (TC) landfalls over the U.S. mid-Atlantic region, which include so-called Sandy-like, or westward-curving, tracks, are among most infrequent along East Coast. However, when these events do occur, resulting economic and societal consequences can be devastating. A recent example is Hurricane Sandy in 2012. Multimodel ensemble seasonal hindcasts conducted with a high-atmospheric-resolution coupled prediction system based on ECMWF operational model (Project Minerva)...

Abstract Boreal winter simulations of the Community Atmospheric Model, version 4.0, were carried out using observed sea surface temperature (SST) fields from three El Niño events 1982/83, 1991/92, and 1997/98 [control (CTL) runs] climatology (CLIM run). In each case, 50 ensemble members run (1 November–31 March). The diabatic heating Q at every grid point, level, day CTL runs in Indo-Pacific region was stored used four additional suites experiments, which parallels appropriate suite. suite,...

Abstract The Indian summer monsoon is partly modulated by persistent remote forcing from the tropical Indo-Pacific, evident in dominant observed teleconnection patterns, namely, El Niño–Southern Oscillation (ENSO) and equatorial Ocean (EQUINOO). In atmosphere, these teleconnections are presumably driven diabatic heating, primarily associated with release of latent heat condensation rainfall. However, coupled atmosphere–ocean models, biases result large systematic errors heating. This study...

Based on the experiments with Coupled Forecast System version 2 (CFSv2), mechanism by which Madden-Julian Oscillation (MJO) modulates North Atlantic (NAO) is investigated. To isolate cyclic MJO heating an eastward propagation over Indian Ocean and western Pacific, three sets of are conducted spatio-temporal varying added to model’s internally generated heating. The results suggest that anomalous Ocean, rather than dominates formation NAO anomaly in following 10-20 days. triggers a westward...