Climatic conditions over the territory of Russia.

By and large, the year 2007 was abnormally warm in Russia. The mean annual air temperature anomaly averaged over the region was 2.0° C (Fig.1).

Fig.1. Anomalies of mean annual air temperature averaged over the Russian territory for 1939-2007 (against norms for 1961-1990).

Last winter and summer were also abnormally warm over the Russian territory, with mean seasonal air temperature anomalies being 3.2° C and 1.8° C, respectively (Fig.2). In spring and fall, mean seasonal air temperature anomalies ranked second for the period in question. For the whole of Russia, in spring and fall, the air temperature anomaly attained 2.2° C and 1.8° C, respectively.

Figure 3 shows anomalies of mean winter air temperatures averaged over quasi-homogeneous climatic regions. In regions 5 and 6, these anomalies ranked second among those in the period considered, being 5.1° C and 3.7° C, respectively.

January in 2007 proved to be abnormally warm over most of Russia. The vast territory of Russia, from its western boundaries to the Lena River, has not experienced such high temperatures for the past 117 years, i.e. for the entire period of regular meteorological observations. As a result, the January of 2007 in Russia has proved to be the warmest since 1891. Severe Atlantic storms moved eastwards and brought warm wet air masses. The Atlantic cyclones broke the predominance of the Siberian anticyclone that became considerably weaker and shifted northeastwards. Therefore, the weather in Siberia was not typical of January. The temperature regime in January 2007 proved to be opposite to that of the last year. In Siberia, that experienced abnormally low air temperatures in January 2006, large heat centers formed (Fig.4). Maximum mean monthly air temperature anomalies were recorded in the northern Krasnoyarsk Territory (over 14° C) and in the southwest of the Yakutia-Sakha Republic (over 12° C). In European Russia, the positive mean monthly air temperature anomalies in the Volga Region and the Southern Urals exceeded 10° C. In the center of European Russia, the first half f January was particularly warm. Many meteorological stations, including those in Moscow, recorded air temperatures higher than diurnal maximums.

Fig.2. Anomalies of mean seasonal air temperature averaged over the Russian territory (deviations from averages for the period 1961-1990).

Fig.3. Anomalies of mean winter (December-February) air temperature averaged over quasi-homogeneous climatic regions for 1939-2007 (deviations from averages for the period 1961-1990).

The regions over which the Atlantic cyclones passed received a large amount of precipitation, except central Western Siberia that was in the “rain shade” provided by the Urals. Many regions in European Russia received more than two monthly norms of precipitation. The highest exceeded monthly norm was recorded downstream the Lena River (over three monthly norms), with monthly winter precipitation norms being low in this region.

Over most of European Russia, February appeared to be the only month to correspond to the genuine winter. Maximum (in absolute value) negative air temperature anomalies are recorded in the east of the northwestern region and in the south of the northern region (-6…-8° C). In the north of Siberia, cold weather was also prevailing. Beginning on February 8, frosts as heavy as -40…-45° C, attaining in places -50…-52° C, were recorded in the south of the Taimyr Autonomous Area, the Krasnoyarsk Territory (the Turukhansk region), and the south of Evenkia. As a result, the mean monthly air temperature proved to be 8-10° C below normal.

Spring temperatures over the Russian territory were higher than the long-term average. The seasonal air temperature anomaly, averaged over the Russian territory, ranked second for the period of record. On the Arctic coast of European Russia and in Western Siberia (region I), a positive anomaly of the mean seasonal air temperature averaged over the region attained a record-breaking value (Fig.5).

In March, especially in its second half, the abnormally warm weather was recorded. At many meteorological stations in central European Russia, absolute daily air temperature maximums were also exceeded. By and large, for most of the stations, March proved to be the warmest throughout the period of record (Fig.6). In the southern Far East, cool and humid weather was caused by deep cyclones that, while moving from the south, brought heavy snowfalls and strong winds. In March, the Maritime Territory experiences heavy snow nearly every year, but this was the first time, when the intensity of snowfalls was so high. At 24 meteorological stations of the Territory, the absolute daily precipitation maximum was exceeded (Fig.7). In March, the Maritime Territory received three to four monthly precipitation norms, the

Fig.4. Air temperature anomalies in January 2007.

Insets show the series of the January air temperature anomaly averaged over the Russian territory and the series of mean January air temperature at meteorological stations Volgograd, Yanov stan, Turukhansk and Olekminsk.

Fig.5. Anomalies of mean spring air temperature averaged over quasi-homogeneous climatic regions for 1939-2007.

southern Khabarovsk Territory received two to three monthly precipitation norms, and Sakhalin received twice as much precipitation as the long-term average. Okhotsk, the southern Khabarovsk Territory, received 62 mm of precipitation, which five times above normal.

April was warm over most of the territory, especially over the Asian territory. Maximum mean monthly air temperature anomalies (higher than 10° C) were recorded in the north of Eastern Siberia and in the Taimyr Autonomous Area. Nearly over the whole of Russia, except Sakhalin and the Southern Federal District, mean monthly air temperatures were above normal, so the April of 2007 has ranked second among the warmest months since 1891.

During the last week of May, abnormally hot and dry weather set in central and southern European Russia. On the last days of the month, the air temperature reached 30-37° C even in the Volga-Vyatka region. Record-breaking diurnal air temperatures, 38-39° C, were recorded in the south of the Volgograd Region and in the north of the Astrakhan Region, which 1-3° C above absolute maximums for this period. Hot weather, combined with significant precipitation deficit, low relative air humidity and strong wind, produced dry winds in these regions. Beginning on May 20, soil drought spread over steppe and sub mountain regions of the Republic of North Ossetia-Alaniya.

Fig.6. Mean monthly and daily air temperatures in March from meteorological stations of central European Russia.

Fig.7. Relation of the precipitation total to the normal value in March 2007. Insets show the series of monthly and daily precipitation totals at meteorological stations Dalnerechinsk, Ternei and Omolon.

By and large, summer over the Russian territory was warmer than the long-term average. Mean seasonal air temperatures were above normal in all quasi-homogeneous regions (Fig.8).

In June, the Southern Federal District experienced precipitation deficit against the background of higher temperature conditions, which contributed to the rapid soil drying-up and the development of soil drought. A combination of soil drought and hot dry weather had an adverse effect on the grain crop. Drought emergency was announced in the Rostov Region and the Republic of Kalmykia. Rains that fell in the region on the last days of June stopped the soil drought that persisted 30 to 45 days.

Hot weather was recorded in the Southern Federal District during most of July, which, in combination with precipitation deficit and low relative air humidity, produced dry winds and drought. A vast heat area, at the center of which mean monthly air temperature anomalies were higher than 6-7° C, formed in Chukotka.

For the Russian territory as a whole, August proved to be the warmest for the period in question (Fig.9). As for European Russia, maximum air temperatures were recorded in the Rostov and Volgograd Regions, where August proved to be the warmest for the past century. Combined with substantial precipitation deficit, this produced air and soil droughts. As for the Asian territory, maximum anomalies were recorded in the northern Far East. For Chukotka and Kolyma, this August proved to be the warmest for the past 107 years. In August, soil drought persisted in individual regions of the Chita Region and the Republic of Buryatia. Productive moisture supplies in the topsoil and one-meter layer reached critical values and on individual fields, the topsoil was dried-up completely.

Fig.8. Anomalies of mean summer air temperature averaged over quasi-homogeneous climatic regions for 1939-2007.

The fall in 2007 was also abnormally warm, particularly on the Arctic coast of Asian Russia (Fig.10).

September was warm throughout the Russian territory. Mean monthly air temperatures were above normal nearly everywhere. The mean September temperature was only a little lower than the record-breaking value of 2005. In individual regions, however, the air temperature attained this value. In northern Chukotka (Pevek), where mean monthly air temperature anomalies were higher than 6° C, September was the warmest for the whole period of record.

In October, mean monthly air temperatures were above normal throughout the Russian territory, except the southern regions of Western and Eastern Siberia and the southwestern coast of Kamchatka. Over most of the country, the increased temperature background persisted for the second consecutive month. Like in September, the highest mean monthly air temperature anomalies in the Far East were recorded in Chukotka, higher than 7° C. In October, it was very warm on the Arctic coast and in southeastern Yakutia. Even in the vicinity of the cold pole, Oimyakon, where the secondary core of the Siberian anticyclone generally begins to be formed in October, mean monthly air temperature anomalies were 5° C above normal. This was due to the effect of the abnormally deep Aleutian depression whose peripheral areas let the warm maritime air arrive at these regions.

Fig.9. Air temperature anomalies in August 2007. Insets show the series of the August air temperature anomaly averaged over the Russian territory and the series of mean monthly and daily air temperatures in August 2007 at meteorological stations Volgograd and Mys Billingsa.

Fig. 10. Anomalies of mean fall air temperature averaged over quasi-homogeneous climatic regions for 1939-2006.

The heat area over the Asian territory also persisted in November. The center of maximum anomalies (higher than 8° C) remained at the same place – in the vicinity of Kolyma and in northern Chukotka. In November, record-breaking temperatures were observed at the cold pole of the Northern Hemisphere, the Oimyakon town (Yakutia). On November 7, the maximum air temperature reached -10.5° C, which was nearly 20° C above climatic normal.

December proved to be warmer than usually over most of Russia. Vast heat areas were formed in the north of European Russia and in the northeast of the Asian territory of the country. Here mean monthly air temperatures were 8 and 10° C above normal, respectively. In Chukotka, where mean monthly air temperature was above normal for the fourth consecutive month, yet another temperature record was broken. At some of the stations (Shmidt Cape, Valkarai), this December became the warmest for the entire history of observations.

The snow state over the Russian territory in the 2006-2007 winter was studied from regular snow observations at 600 Russian meteorological stations.

To estimate the snow cover duration, the number of days, when more than 50% of the territory around a meteorological station was covered with snow, was used.

Fig.11. Anomalies of the number of days when more than 50% of the territory around a meteorological station was covered with snow for the 2006-2007 winter (against long-term averages for 1961-1990). Insets show: a) first dates with snow covering over 50% of the surrounding territory and daily averages of the extent of snow covering the territory around the meteorological station for Kostroma (27333) and Kandalaksha (22217).

Positive values that are no more than 20 days are prevailing in the spatial distribution of snow duration anomalies in the 2006/2007 winter (Fig.11). However, a very warm start of the winter season over European Russia (even in Karelia and on the Kola Peninsula, November and December air temperatures were positive or close to zero) resulted in the fact that no snow cover was recorded in the mean long-term period. This caused significant negative anomalies in the snow duration in western and northwestern European Russia.

Fig.12. Anomalies of maximum snow depth in the 2006-2007 winter (against long-term averages for 1961-1990). Insets show mean daily air temperatures, extent of snow covering the vicinity of the meteorological station, snow depth and daily precipitation total at meteorological stations Ayan (31168) and Turukhansk (23472).

Nearly everywhere in European Russia, except extreme northeastern regions and the Urals, the snow depth was below normal (Fig.12).

In Asian Russia, the following areas experienced maximum snow depth of more than 100 cm: northern Krasnoyarsk Territory, Perm Region, northern and western coasts of the Sea of Okhotsk, as well as small areas in the Sayan Mountains and on the eastern coast of Kamchatka (Fig.13).

Fig.13. Maximum snow depth in the 2006-2007 winter.

Extremely warm weather that was observed in the northern Krasnoyarsk Territory in January contributed much to the formation of positive snow height anomalies in this region (Figs 12, 13). Severe Atlantic cyclones penetrated deep into the continent bringing warm and wet air. In January, this region received more than two precipitation norms.

Due to heavy snowfalls at some of the meteorological stations of the Sea of Okhotck, the snow height as early as November reached 90 cm. Meteorological station Ayan (Fig.12) recorded 188.9 cm of precipitation from 6 to 11 November, which is five times higher than monthly normal. In the subsequent winter months, precipitation was nearly not recorded. In March, weather in the region was affected by several southern cyclones that brought warmer weather, snowfalls and snowstorms (see March precipitation, Fig.7).