Mid-latitude Asia Research Articles

A sudden change in summer rainfall characteristics in Korea during the late 1970s

AbstractWe have examined long‐term climate change in Korea by studying daily rainfall data over a period of 48 years (1954–2001). The results show that there is a more frequent heavy rainfall anomaly larger than 100 mm per 3 months in recent years. For further investigation, we divide the whole period into two 24 year intervals, 1954–77 and 1978–2001. Two well‐defined rainfall peaks occur during summertime in both intervals. During the earlier interval, primary and secondary rainfall peaks are found in early July and early September, respectively. In the later interval, on the other hand, the secondary peak is found in mid–late August, mainly attributed to enhanced heavy rainfall (≥30 mm day−1) events. Although a similar shift occurs in the primary peak, it is much smaller. Thus, the relatively dry spell between the two peaks becomes shorter in the later interval compared with the earlier one.The domain‐mean geopotential height at 700 hPa (Φ700) over mid‐latitude Asia (30–50° N, 60–120° E) for the summer also experienced a sudden increase in the mid 1970s. A comparison of the spatial distribution of Φ700 between the two intervals shows large positive differences over the central‐eastern Asian continent in the later interval. In contrast to the positive anomaly of Φ700 in the later interval, there is a decreasing trend in surface temperature. The increased Φ700 introduces a stronger northerly wind over East Asia and possibly produces a moisture convergence, enhanced convective activity, and heavy rainfall over the region, in particular over Korea and central China. Copyright © 2003 Royal Meteorological Society.

A mid‐latitude Asian circulation anomaly pattern in boreal summer and its connection with the Indian and East Asian summer monsoons

AbstractUsing the NCEP–NCAR reanalysis for 1948–98, this study identifies a dominant pattern for the interannual variation of upper‐level winds over mid‐latitude Asia in boreal summer. This pattern, called the mid‐latitude Asian summer (MAS) pattern, features two anomalous anticyclones: one centred at 37.5° N, 65° E and the other at 42.5° N, 130° E. The MAS pattern significantly influences East Asian summer monsoon variability. In the positive phase of the MAS pattern, contrasting meridional wind anomalies between eastern China and Japan lead to above‐ and below‐normal summer rainfall in north China and south Japan respectively. The year‐to‐year change of the MAS pattern is related to that of the Indian summer rainfall, especially in central and northern India. Thus, the MAS pattern plays a role in connecting anomalous Indian heating with the East Asian summer monsoon variability.The East Asian anomalous anticyclone displays a southeastward shift after the late 1970s. This results in a similar change of anomalous summer rainfall regions in East Asia. The West Asian anomalous anticyclone moves northeastward after the late 1970s. The relation of the MAS pattern with the Indian summer rainfall experienced an obvious weakening in the late 1970s. As a result, the statistical relation between the Indian and north China summer rainfall becomes weak after the late 1970s. Copyright © 2002 Royal Meteorological Society

The weakening of the Asian monsoon circulation after the end of 1970's

The transition of the global atmospheric circulation in the end of 1970's can clearly be detected in the atmospheric temperature, wind velocity, and so on. Wavelet analysis reveals that the temporal scale of this change is larger than 20 years. Studies in this work indicate that the trend of the transition over the mid-latitude Asia is opposite to that of global average for some variables at the middle troposphere. Another finding of this research is that the African-Asian monsoon circulation is weaker and the trade wind over the tropical eastern Pacific is weaker as well after this transition. Such a signal may be found in the summer precipitation over China as well.

Timing of late Quaternary vegetation response in the 30–50° latitude bands in southeastern Australia and northeastern Asia

Abstract Quaternary climatic change in part results from Milankovitch forcing, and is accordingly a boundary condition commonly applied in global climate modelling. Orbital parameters result in different receipts of insolation across a year, and result in hemispheric differences in climate, for example, in the seasonal expression of climate. This effect may be dampened by the effects of the ocean, topographic and other forcing factors. In this study a comparison is made of the late Quaternary records from mid-latitude southeastern Australia and northeastern Asia along the Pole-Equator-Pole (PEP-II) transect of the Australasian hemisphere. A review of the major climate features and vegetation of the regions is given. The study areas have a good geographic coverage of palaeoecological sites and from these it is possible to estimate the timing of the major vegetation shifts over the last 25,000 years; including through the period of Last Glacial Maximum, recovery from this to events around the Pleistocene-Holocene transition, and the timing of peak warming in the Holocene. There appears to be no difference in the timing of vegetation response in the two regions at Last Glacial Maximum or around the Pleistocene-Holocene boundary. However, the peak of Holocene warming appears to significantly precede its expression in southeastern Australia. Data from all periods show significantly different variations in responding to climate change along the PEP-II transect. These findings have to be considered in relation to the range and quality of the existing records, and in the great differences in taxonomy and community structure between the two regions.