Anthony R. Lupo

Studying Summer Season Drought in Western Russia

During the 2010 summer, a severe drought impacted Western Russia, including regions surrounding Moscow and Belgorod (about 700 km south of Moscow). The drought was accompanied by high temperatures. Moscow recorded 37.8°C (100°F) for the first time in over 130 years of record keeping. The record heat, high humidity, dry weather, and smoke from forest fires caused increased human mortality rates in the Moscow region during the summer. The excessive heat and humidity in Western Russia were the result of atmospheric blocking from June through mid-August. The NCAR-NCEP reanalyses were used to examine blocking in the Eastern European and Western Russia sector during the spring and summer seasons from 1970 to 2012. We found that drier years were correlated with stronger and more persistent blocking during the spring and summer seasons. During these years, the Moscow region was drier in the summer and Belgorod during the spring seasons. In the Moscow region, the drier summers were correlated with transitions from El Nino to La Nina, but the opposite was true in the Belgorod region. Synoptic flow regimes were then analyzed and support the contention that dry years are associated with more blocking and El Nino transitions.

Trends in Summer Season Climate for Eastern Europe and Southern Russia in the Early 21st Century

The goal of this research is to evaluate changes in temperature and precipitation in the Central Chernozem Region of southwestern Russia during the summer and relate these to large-scale circulation types and synoptic circulation processes. Some of these circulation regimes result in extreme weather conditions over the region. Using a classification system for Northern Hemisphere large-scale flow regimes and observations of weather within the Central Chernozem Region, the role of individual synoptic patterns in the formation of weather anomalies was identified. Also, comparing the periods 1981–2010 and 1971–2000, the mean summer temperatures increased by 0.6°C regionally. During the most recent decade the increase was 1.3°C. Total precipitation for the summer increased over the 20th century and was characterized by less variability during the second half when compared to the first half. However, in the beginning of the 21st century, precipitation has decreased during the growing season, but variability has increased. The increase in summer temperatures and increased variability in precipitation were then linked to an increase in the occurrence of weather regimes associated with warm anomalies and blocking. Finally, the results of this study can be used to translate larger-scale seasonal or climate forecasts to the regional scale.

The occurrence of extreme monthly temperatures and precipitation in two global regions

ABSTRACT Recently, there has been focus on extreme weather events and the connection to climate change and weather variability. Most work is related to individual events rather than mean monthly conditions. This study examines the occurrence of extreme monthly temperature and precipitation events in the central United States (cUSA) and southwest Russia (swRUS). The surface data were provided by the Missouri Climate Center and the Russian Hydrometeorological Center for an extended period (126 years for cUSA and 71 years for swRUS). An extreme event is defined such that a large enough sample is gathered without losing the meaning of extreme. The results demonstrate that in cUSA, there was no preference for warm or cold anomalies. For swRUS, there was a preference for cold (warm) anomalies early (late) in the period, which was characterized by steadily increasing temperatures. There was a tendency in both locations for extreme months during a preferred phase of the El Niño Southern Oscillation. In both regions, there was no significant signal in extreme temperature related to longer term climatic cycles, whereas for precipitation there was a relationship to the Pacific Decadal Oscillation for cUSA. Additionally, cold monthly anomalies were associated with persistent and strong upstream blocking events. Finally, two case studies are examined for the cUSA.

Evolution of the Water Vapor Plume over Eastern Europe during Summer 2010 Atmospheric Blocking

We present an analysis of water vapor (WV) plume evolution over Eastern Europe (EE) during atmospheric blocking in the summer of 2010, carried out on the basis of satellite (MODIS and MLS instruments), aerological, and NCEP/NCAR reanalysis data. The obtained results show that the development of blocking was accompanied by the development of a positive anomaly of total column water vapor (TCWV) content over the northern part of EE. Local TCWV content from 28 July to 6 August 2010 reached 3.35 cm, a value that exceeded by 3.3 times its content before the block. The surplus of WV was mainly conditioned by the advection of WV due to transfer of moist air from the Atlantic Ocean and the Mediterranean Sea into northern EE and also due to increased evaporation from the surface enriched with water due to increased temperature and wind. We hypothesize that the influx of latent heat in the block area can contribute to the energy supply of the blocking anticyclone and prolong the existence of block. Strong humidification of the troposphere and some dehumidification of the lower stratosphere during the block were accompanied by warming of the troposphere and cooling of the lower stratosphere.

Using Enstrophy-Based Diagnostics in an Ensemble for Two Blocking Events

Recent research has used enstrophy-based diagnostics to identify the development and dissipation stages of blocking events. These previous studies made use of reanalysis data sets in the calculations of the enstrophy-based diagnostics, such as the NCEP-NCAR reanalysis (2.5° × 2.5°) of geopotential height and horizontal winds. However, none of these studies has explored the use of the enstrophy-based diagnostics in weather or climate models with higher horizontal resolution. In this paper, the enstrophy-based diagnostics are used to analyze two blocking events, using data from the ERA-Interim reanalysis data set (0.75° × 0.75°) and also the Global Ensemble Forecast System (GEFS) (1° × 1°). The results of this work indicate that using an ensemble may be more effective than a single dynamical control forecast in evaluating the enstrophy-based diagnostic quantities, and that the results are similar to those obtained with coarser resolution.

A response in the ENSO cycle to an extratropical forcing mechanism during the El Niño to La Niña transition

Current El Niño-Southern oscillation (ENSO) theory emphasizes that the forcing that drives the cycle mainly exists within tropical regions. However, these ideas are quite limited in explaining completely the occurrence of ENSO. Here, we examine whether extratropical forcing can affect ENSO cycle, specifically the transition from El Niño to La Niña. Although dispersion of the Okhotsk-Japan (OKJ) atmospheric wave train across the mid-latitude North Pacific during June terminates in the subtropics, the associated regime of southward surface wind anomalies could reach Eastern Equatorial Pacific (EEP). The OKJ wave train plays a substantial role in generating a similar underlying sea surface temperature (SST) wave train through a barotropic process in air–sea interactions and after September, it is negatively correlated strongly with the SST around EEP. Strong OKJ propagation in the positive (negative) phase during June is more (less) significantly associated with a subsequent La Niña (El Niño) episode that is matured after October. Negative SST anomalies at the southern end of the SST wave train with strong overlying OKJ propagation in the positive phase during June and the associated southward surface wind anomalies retained its strength by the further infusion of energy and gradual southward displacement joining the negative SST anomalies around EEP after the October when La Niña usually matured in-situ. Strong OKJ propagation in the positive phase during June tends to occur during a quick summer and fall transition period from El Niño to La Niña. This study strongly suggests that extratropical forcing plays an ignored role in affecting ENSO cycle especially in the formation of La Niña, which was not included in current ENSO theory.

What does the APO mean

The Asian–Pacific Oscillation (APO) is a relatively new teleconnection index and a number of peer-reviewed studies have confirmed its’ existence. This study reexamines the concept of the APO teleconnection as currently published in the literature. Most results have found that this pattern could be defined as its own teleconnection pattern within the Pacific Ocean Basin. This work demonstrates that the APO is inevitably associated with an additional action centre located over the North Atlantic Ocean, and the index can be extended. Previous studies have used a variety of methods to represent the APO, and a method is proposed here to standardise the formulation. It is argued that the extended index proposed here provides a more robust result. The APO typically is identified using the eddy temperature rather than geopotential height as the source material for its construction, as geopotential could not adequately represent this teleconnection pattern. This leads to a discussion regarding the basic criterion for defining teleconnective activity within the extratropical regions. We also identify other problems in the current understanding of APO theory that need to be addressed.