Search

In this paper, the effects of spring soil moisture (SM) anomalies in the mid‐latitudes on the atmospheric circulation in summer over the Northern Hemisphere (NH) are investigated. The results show that there are two regions of maximum interannual variability of the spring SM in the mid‐latitudes, which are located in central North America (CNA) and Europe and central Asia (ECA). In addition, the interannual variation of spring SM anomalies between CNA and ECA exhibits a seesaw pattern. The CNA–ECA seesaw pattern of the spring SM anomalies leads to the surface heat anomalies having opposite phases in CNA and ECA from spring to summer, which subsequently cause the opposite phase of baroclinicity anomalies in spring. The anomalous meridional temperature advections in spring cause the baroclinicity anomalies to have the same phase around CNA and ECA in summer. Corresponded with the same phase of baroclinicity anomalies, the anomalous centers of the stationary Rossby wave train (RWT) and Rossby wave source (RWS) have the same phase in CNA and ECA in summer. Through analysis of the vorticity budgets, the maintenance mechanism of the RWT in summer is considered as a positive feedback that anomalous meridional winds characterized by a RWT, transport the mean absolute vorticity and subsequently lead to an anomalous RWS, which in turn maintains the stationary RWT. Numerical experiments further demonstrate the effects of CNA–ECA seesaw pattern of spring SM anomalies on stationary RWT and RWS in summer. Plain Language Summary: The interannual variation of soil moisture (SM) anomalies in mid‐latitudes exhibits a seesaw pattern in central North America (CNA) and Europe and central Asia (ECA). When spring SM anomalies are negative in CNA and positive in ECA, positive (negative) sensible heat flux anomalies are observed in CNA (ECA) while negative (positive) latent heat flux anomalies are observed in CNA (ECA) from spring to summer, or vice versa. Influenced by surface heat anomalies, baroclinicity anomalies exhibit a seesaw pattern in CNA and ECA in spring, and have same phase in CNA and ECA in summer due to anomalous meridional temperature advections. The baroclinicity anomalies in CNA and ECA in summer contribute to the same variation of wave‐flow interactions. The Rossby wave train (RWT) induced and maintained by CNA–ECA seesaw pattern of spring SM anomalies in spring can be maintained by its meridional transportation of the mean absolute vorticity in summer. Apparently, spring SM anomalies in the middle latitudes can persistently influence the large‐scale atmospheric circulations over the Northern Hemisphere by maintaining RWT. Key Points: Seesaw pattern of spring soil moisture anomalies in central North America (CNA) and Europe and central Asia (ECA)Baroclinicity anomalies change from opposite to same phase in CNA and ECA during the transition from spring to summerRossby wave train induced by spring CNA–ECA seesaw pattern is maintained by its meridional mean absolute vorticity transportation in summer [ABSTRACT FROM AUTHOR]

Most papers on the physical condition of birds during spring migration focused on food availability preceding migratory take-off. Only a few studies examined the effect of climate conditions at the wintering grounds upon autumn arrival on bird physical condition later on. Here, we hypothesized that environmental conditions upon arrival at the wintering grounds, and not necessarily upon departure, have a crucial carry-over effect on bird spring migration. Using 29,000 observations of the lesser whitethroat, Sylvia curruca, and the eastern Bonelli’s warbler, Phylloscopus orientalis, we found temperatures upon arrival at the African wintering grounds to be the only climatic variable correlated with birds’ body state upon spring stopover in Israel, six months later. Two different mechanisms could explain these results. One possibility is that high temperatures create favorable conditions for insect activity, which allows rapid recovery from autumn migration and hence successful winter survival and maintenance. Another possible scenario is that harsh conditions, due to the heat and dry environment, cause high mortality, permitting survival of larger individuals which, then, enjoy reduced inter- and intra-specific competition. Whatever the mechanism is, our findings suggest that conditions upon autumn arrival, and not necessarily at the end of winter as traditionally thought, may have a major impact on migrating birds. [ABSTRACT FROM AUTHOR]

Instruments for air quality observations on geostationary satellites provide multiple observations per day and allow for the analysis of the diurnal variation of important air pollutants such as nitrogen dioxide (NO2) over large areas. The South Korean instrument GEMS on the GK2B satellite was launched in February 2020 and is the first instrument in geostationary orbit that delivers hourly daytime observations of NO2. The measurements with a spatial resolution of 3.5 km x 8 km cover a large part of Asia. This study compares one year of tropospheric NO2 vertical column density (VCD) observations of the operational GEMS L2 product, the scientific GEMS IUP-UB product, the operational TROPOMI product, and ground-based DOAS measurements in South Korea. The GEMS L2 tropospheric NO2 VCDs overestimate the VCDs retrieved from the ground-based observations with a median relative difference of +64 % and a correlation coefficient of 0.75. The median relative difference is -1 % for the GEMS IUP-UB product and -14 % for the TROPOMI product. The evaluation of the GEMS IUP-UB product and the operational TROPOMI product with ground-based measurements is in good agreement with correlation coefficients of 0.82 and 0.88. The scatter in the GEMS products can be reduced when observations are limited to the TROPOMI overpass time. The observed diurnal variations of the tropospheric NO2 VCDs show a maximum of NO2 during the late morning for urban sites, whereas rural sites show weak or almost no diurnal changes. Investigations of the seasonal diurnal variability show with a minimum in the observed tropospheric NO2 VCDs around noon the importance of chemical loss of NO2 in summer. Most variability is seen in spring and autumn, which dominate the average annual diurnal cycle. Observations under low wind conditions show strong enhancements of NO2 over the day, especially at polluted sites during winter. This indicates that under calm conditions, dilution and the less effective chemical loss in winter do not balance the accumulating emissions. The impact of transport processes is illustrated by the diurnal variability at a rural site following mean wind patterns for specific seasons and observation times. Analyzing the weekday-weekend effect, good agreement was found between the different products. However, the GEMS L2 product while agreeing with the other data sets during weekdays shows significantly less reduction on weekends. Our investigations show that the observed diurnal evolution of NO2 varies significantly at the different measurement sites, with good agreement between the GEMS IUP-UB and ground-based observations. The diurnal variability of tropospheric NO2 VCDs depends on chemistry, emissions, and transport into and out of the measurement region. To interpret the sources and sinks of NO2 requires that all of these factors are considered. [ABSTRACT FROM AUTHOR]

Present study investigates the characteristics and factors of summer drought variations over Asia during 1950–2020 using 3-month Standardized Precipitation Evapotranspiration Index (SPEI03) in July. The leading mode of Asian summer drought variations exhibits a roughly north–south contrasting distribution across 30° N with dominant interannual variability. The interannual variation of the leading mode is associated with both precipitation and temperature. In comparison, the contribution of precipitation is larger in the eastern part of the mid-latitude Asia. The Asian summer drought variations subject to both individual and combined impacts of preceding winter equatorial central-eastern Pacific (ECEP) sea surface temperature (SST) anomalies and concurrent North Atlantic (NA) tripole SST anomalies. Preceding ECEP SST anomalies induce anomalous vertical motion and precipitation over the mid-latitude Asia through large-scale divergence and convergence in previous winter and spring. The resulted soil moisture anomalies persist to summer and are conducive to anomalous summer precipitation through evaporation. The accompanying changes in cloud-radiation, surface longwave radiation and sensible heat flux induce temperature and evapotranspiration anomalies. The NA tripole SST anomalies induce anomalous vorticity forcing over the western mid-latitude NA. This contributes to a wave train that propagates from the NA to East Asia and affects wind and vertical motion over the mid-latitude Asia. [ABSTRACT FROM AUTHOR]

Cutoff lows are often associated with high-impact weather; therefore, it is critical that operational numerical weather prediction systems accurately represent the evolution of these features. However, medium-range forecasts of upper-level features using the Global Forecast System (GFS) are often subjectively characterized by excessive synoptic progressiveness, i.e., a tendency to advance troughs and cutoff lows too quickly downstream. To better understand synoptic progressiveness errors, this research quantifies seven years of 500-hPa cutoff low position errors over the globe, with the goal of objectively identifying regions where synoptic progressiveness errors are common and how frequently these errors occur. Specifically, 500-hPa features are identified and tracked in 0–240-h 0.25° GFS forecasts during April 2015–March 2022 using an objective cutoff low and trough identification scheme and compared to corresponding 500-hPa GFS analyses. In the Northern Hemisphere, cutoff lows are generally underrepresented in forecasts compared to verifying analyses, particularly over continental midlatitude regions. Features identified in short- to long-range forecasts are generally associated with eastward zonal position errors over the conterminous United States and northern Asia, particularly during the spring and autumn. Similarly, cutoff lows over the Southern Hemisphere midlatitudes are characterized by an eastward displacement bias during all seasons. Significance Statement: Cutoff lows are often associated with high-impact weather, including excessive rainfall, winter storms, and severe weather. GFS forecasts of cutoff lows over the United States are often subjectively noted to advance cutoff lows too quickly downstream, and thus limit forecast skill in potentially impactful scenarios. Therefore, this study quantifies the position error characteristics of cutoff lows in recent GFS forecasts. Consistent with typically anecdotal impressions of cutoff low position errors, this analysis demonstrates that cutoff lows over North America and central Asia are generally associated with an eastward position bias in medium- to long-range GFS forecasts. These results suggest that additional research to identify both environmental conditions and potential model deficiencies that may exacerbate this eastward bias would be beneficial. [ABSTRACT FROM AUTHOR]

Climate-driven changes in precipitation amounts and their seasonal variability are expected in many continental-scale regions during the remainder of the 21st century. However, much less is known about future changes in the predictability of seasonal precipitation, an important earth system property relevant for climate adaptation. Here, on the basis of CMIP6 models that capture the present-day teleconnections between seasonal precipitation and previous-season sea surface temperature (SST), we show that climate change is expected to alter the SST-precipitation relationships and thus our ability to predict seasonal precipitation by 2100. Specifically, in the tropics, seasonal precipitation predictability from SSTs is projected to increase throughout the year, except the northern Amazonia during boreal winter. Concurrently, in the extra-tropics predictability is likely to increase in central Asia during boreal spring and winter. The altered predictability, together with enhanced interannual variability of seasonal precipitation, poses new opportunities and challenges for regional water management. This study shows that climate change will alter the sea surface temperature - precipitation relationships and our ability to predict seasonal precipitation by 2100. [ABSTRACT FROM AUTHOR]

The microsporidian, Nosema maddoxi Becnel, Solter, Hajek, Huang, Sanscrainte & Estep, infects brown marmorated stink bug, Halyomorpha halys (Stål) (Hemiptera: Pentatomidae), populations in North America and Asia and causes decreased fitness in infected insects. This host overwinters as adults, often in aggregations in sheltered locations, and variable levels of mortality occur over the winter. We investigated pathogen prevalence in H. halys adults before, during, and after overwintering. Population level studies resulted in detection of N. maddoxi in H. halys in 6 new US states, but no difference in levels of infection by N. maddoxi in autumn versus the following spring. Halyomorpha halys that self-aggregated for overwintering in shelters deployed in the field were maintained under simulated winter conditions (4°C) for 5 months during the 2021–2022 winter and early spring, resulting in 34.6 ± 4.8% mortality. Over the 2020–2021 and 2021–2022 winters, 13.4 ± 3.5% of surviving H. halys in shelters were infected with N. maddoxi , while N. maddoxi infections were found in 33.4 ± 10.8% of moribund and dead H. halys that accumulated in shelters. A second pathogen, Colletotrichum fioriniae Marcelino & Gouli, not previously reported from H. halys , was found among 46.7 ± 7.8% of the H. halys that died while overwintering, but levels of infection decreased after overwintering. These 2 pathogens occurred as co-infections in 11.1 ± 5.9% of the fungal-infected insects that died while overwintering. Increasing levels of N. maddoxi infection caused epizootics among H. halys reared in greenhouse cages after overwintering. [ABSTRACT FROM AUTHOR]

The sudden swings between drought/heat and pluvial could cause adverse impacts far surpassing the sum of their individual effect. We propose a concept of intraseasonal "compound whiplash event" (CWE) to investigate sudden swings between wet and the compounding warm‐dry events and their changes under climate change. We find that global warming would likely escalate the compound whiplash frequency to two to three and half times (two to three times) by the end of the 21st century under the business‐as‐usual scenario (mitigated scenario). The growing threat of CWE not only stems from the increasing occurrence but also from its intensified severity and extended spatial coverage. Among all sub‐regions, East Asian summer monsoon (EASM) region would expect the largest intensification. The resulting population exposure would soar two‐to‐three‐fold over Asia. Populous regions such as North India and EASM region might face a much worse situation than the western China where population is sparse and projected to decline. Moreover, the seasonality of swings with opposite directions would further split as a response to the skewed Asian monsoon annual cycle, leading to more frequent heat‐drought to pluvial swings in spring, and more opposite‐direction swings in autumn, disrupting cultivation and water management convention. Plain Language Summary: Either drought/heat or pluvial already causes adverse impacts on ecosystem and human society. The swing between these extremes could escalate their impact to the next level, far beyond their simple addition. Though some studies have investigated weather whiplash on longer time scales, such as months to years, intraseasonal whiplashes on an event basis are rarely explored. Hence, we propose a concept of "compound whiplash event" to investigate the intraseasonal alternation between warm‐dry and wet conditions and their potential changes in a warmer future climate. We find that global warming not only leads to one‐to‐two and half times more compound weather whiplashes by the end of 21st century under the business‐as‐usual scenario, but also intensifies their severity and extends their extent. Within Asia, East Asian summer monsoon region will likely face the largest increase. As a result, the population exposed to the compound weather whiplash would double or even triple, especially in the populous regions with further population growth. In addition, with skewed Asian monsoon annual cycle, the seasonality of swings expects a coherent shift, that is, more heat‐drought swings in spring and more opposite‐direction swings in autumn, potentially posing more disruption in agricultural and water management activities. Key Points: Intraseasonal compound weather whiplash in Asia is introduced and defined using a 3D event‐based approachCompound weather whiplash is projected to triple with intensified severity and shifted seasonality by the end of the 21st centurySouthern and eastern Asia will see the most increase in population exposure while population decline tempers the increase elsewhere [ABSTRACT FROM AUTHOR]

Absorbing aerosols, consisting of smoke (black carbon (BC) and other organics) and dust (from windblown sources), can have a strong warming effect on the climate and impact atmospheric circulation due to localized heating. To investigate the spatiotemporal and vertical changes of absorbing aerosols across Asia, collocation data from OMI, MODIS, and CALIPSO were used to compare two periods: 2006–2013 and 2014–2021. This study revealed a significant temporal and spatial contrast of aerosol loading over the study region, with a drop in total aerosol concentration and anthropogenic smoke concentration recorded across the Eastern China region (all seasons) and a concurrent increase in the Indian sub-continent region (especially in autumn). The range of aerosol diffusion is affected by the height of the smoke and aerosol plumes, as well as the wind force, and is dispersed eastwards because of the Hadley circulation patterns in the Northern Hemisphere. Smoke from Southeast Asia typically rises to a height of 3 km and affects the largest area in contrast to other popular anthropogenic zones, where it is found to be around 1.5–2 km. The dust in Inner Mongolia had the lowest plume height of 2 km (typically in spring) compared to other locations across the study region where it reached 2–5 km in the summer. This study showed, by comparison with AERONET measurements, that combining data from MODIS and OMI generates more accuracy in detecting aerosol AOD from smoke than using the instruments singularly. This study has provided a comprehensive assessment of absorbing aerosol in Asia by utilizing multiplatform remote-sensed data and has summarized long-term changes in the spatiotemporal distribution and vertical structure of absorbing aerosols. [ABSTRACT FROM AUTHOR]

Mungbean (Vigna radiata L.), one of the most widely grown edible legumes in Asia, plays important roles in the improvement of agricultural cultivation systems as well as human diets. As an understudied crop, however, most mungbean varieties are characterized by unstable yields, poor disease resistance, and unsuitability for mechanical harvesting, thereby leading to a low production income. We, therefore, developed Jilv 20, a new mungbean cultivar with a dull seed coat, by crossing Bao 942-34 with Weilv 9002-341. After 11 years of selection and evaluation, Jilv 20 has shown wide adaptability, early maturity, high yield, halo blight resistance, and suitability for mechanical harvesting. The growth period of Jilv 20 is 79.5 and 66.7 days in the spring and summer sowing seasons, respectively, and the average plant height is approximately 56.4 cm. In this study, average yields were 1737.9, 1532.3, and 2045.1 kg/hm2 in northern spring-sowing, northern summer-sowing, and southern sites, respectively; these values were respectively 27.83%, 28.48%, and 6.96% higher than those of control cultivar Zhonglv 5, which has been popular in past decades because of its wide adaptability. The average protein and starch contents of Jilv 20 seeds were 25.0% and 49.56%, respectively. Further application and extension of Jilv 20 in China should contribute to mungbean production, breeding, and industrial development. [ABSTRACT FROM AUTHOR]

Upon analysing the global distribution of the highest 2 % of daily CO mixing ratios at 400 hPa derived from the MOPITT satellite instrument for 20 years (2000–2019), we very regularly detect regions with very high CO values (i.e. mixing ratios belonging to the globally highest 2 %) over the remote Northern Hemispheric (NH) Pacific. Such events of elevated CO over the upper tropospheric NH Pacific occur throughout the year with surprisingly high regularity and frequency (70 % of all days during winter, 80 % of all days during spring). During winter, most of these pollution events are detected over the north-eastern and central NH Pacific, during spring over the central NH Pacific, and during summer over the western NH Pacific. We detect most pollution events during spring. To link each individual pollution event detected by the 2 % filtering method with a specific CO source region, we perform trajectory calculations using MPTRAC, a Lagrangian transport model. To analyse transport pathways and uplift mechanisms, we combine MOPITT data, the trajectory calculations, and ERA-Interim reanalysis data. It becomes apparent that air masses from China that are lifted along a frontal system into the free troposphere are the major CO source throughout the year. The contributions of other source regions and uplift mechanisms show a strong seasonal cycle: NE Asia in combination with upward transport of air masses in the warm conveyor belt of a midlatitude cyclone is a significant CO source region during winter, spring, and summer, while India is an important source region mainly during spring and summer and SE Asia mainly during spring. [ABSTRACT FROM AUTHOR]

Seasonality of suicidal behavior has been widely reported in many epidemiological studies with a well replicated suicide peak in spring followed by a trough in winter season. Research from some regions over the past few decades has shown a diminishing seasonal pattern of suicides and this introduced a new perspective on the suicide study. Data on all suicide deaths from the period 1991 to 2015 was extracted from the South Korean National Death Registration data set which was made available by Statistics Korea. Our findings confirmed a strong seasonal effect of suicides in South Korea throughout the study period and a marked diminishing pattern was observed since the period of 2006–2010. The rhythm of suicides kept changing across the time intervals with a spring peak followed by a second peak in late summer/autumn. The seasonality varied across age groups and the seasonal effect among the Korean elderly suicides was still found to be significant though a diminishing pattern was observed recently. [ABSTRACT FROM AUTHOR]

We use satellite observations from IASI (Infrared Atmospheric Sounding Interferometer) on board the MetOp-A satellite to evaluate the springtime daily variations in lower-tropospheric ozone over east Asia. The availability of semi-independent columns of ozone from the surface up to 12 km simultaneously with CO columns provides a powerful observational data set to diagnose the processes controlling tropospheric ozone enhancement on synoptic scales. By combining IASI observations with meteorological reanalyses from ERA-Interim, we develop an analysis method based only on IASI ozone and CO observations to identify the respective roles of the stratospheric source and the photochemical source in ozone distribution and variations over east Asia. The succession of low- and high-pressure systems drives the day-to-day variations in lower-tropospheric ozone. A case study analysis of one frontal system and one cut-off low system in May 2008 shows that reversible subsiding and ascending ozone transfers in the upper-troposphere-lower-stratosphere (UTLS) region, due to the tropopause perturbations occurring in the vicinity of low-pressure systems, impact free and lower-tropospheric ozone over large regions, especially north of 40° N, and largely explain the ozone enhancement observed with IASI for these latitudes. Irreversible stratosphere-troposphere exchanges of ozone-rich air masses occur more locally in the southern and southeastern flanks of the trough. The contribution to the lower-tropospheric ozone column is difficult to dissociate from the tropopause perturbations generated by weather systems. For regions south of 40° N, a significant correlation has been found between lower-tropospheric ozone and carbon monoxide (CO) observations from IASI, especially over the North China Plain (NCP). Considering carbon monoxide observations as a pollutant tracer, the O3-CO correlation indicates that the photochemical production of ozone from primary pollutants emitted over such large polluted regions significantly contributes to the ozone enhancements observed in the lower troposphere via IASI. When low-pressure systems circulate over the NCP, stratospheric and pollution sources play a concomitant role in the ozone enhancement. IASI's 3-D observational capability allows the areas in which each source dominates to be determined. Moreover, the studied cut-off low system has enough potential convective capacity to uplift pollutants (ozone and CO) and to transport them to Japan. The increase in the enhancement ratio of ozone to CO from 0.16 on 12 May over the North China Plain to 0.28 over the Sea of Japan on 14 May indicates photochemical processing during the plume transport. [ABSTRACT FROM AUTHOR]

We describe a first attempt of wide-area dendroclimatic reconstruction, based upon seven spring temperaturesensitive chronologies from the ring widths of living trees, in Japan and Korea. Mean March-May temperature derived from a gridded land air temperature dataset (CRUTEM4) between 35-40° N and 125-140° E was reconstructed for the period of AD1784-1990. Of the seven, two Japanese chronologies were eliminated during the calibration trials. The reconstruction accounted for 19.4% of the temperature variance in the calibration period, and is considered to be skillful for estimating interannual-to-interdecadal variations and not for long-term change. This reconstruction showed remarkably similar fluctuations to regional dendroclimatic reconstructions in Japan and Korea, indicating the past spatial coherency of spring temperatures in the region. The reconstruction was validated against other climate proxies. A fairly good agreement was found with cold periods as estimated from documentary records in southeast China and Japan. The west Japan temperature series recovered from instrumental records also showed a reasonable agreement with the reconstruction. On the other hand, the reconstruction did not show clear abrupt depressions after the Laki and the Tambora eruptions. These comparisons revealed that dendroclimatic spatial reconstruction in this area offers a good potential for reconstructing long-term and large-scale past temperature patterns for northeast Asia. [ABSTRACT FROM AUTHOR]

The urban heat island effect, classically associated with high impervious surface area (ISA), low vegetation fractional cover (Fr), and high land surface temperature (LST), has been linked to changing patterns of vegetation phenology, especially spring growth. In this study, a collaboration with the Global Learning and Observations to Benefit the Environment (GLOBE) program, we investigated the effect of the urban environment on the timing of leaf budburst of native deciduous trees in seven cities: Asia (Tokyo, Japan; Bangkok and Korat, Thailand), Europe (Jyväskylä, Finland; Bishkek, Kyrgyzstan), Africa (Dakar, Senegal), and North America (Fairbanks, Alaska). The cities differed not only in population size but also in climate and vegetation type. Using Landsat satellite imagery from each city, we calculated LST, Fr, and ISA, and classified sites within each study area as rural or urban. The timing of leaf flushing, measured by students using GLOBE budburst protocols, was statistically different within all cities, with absolute differences ranging from 1 to 23 days. We assessed the classic urban phenology paradigm, which proposes higher LST, lower Fr, and earlier budburst in urban areas of temperate cities. Of the four temperate cities, Tokyo followed the classic paradigm, but no other city demonstrated consistent support. Urban budburst was advanced in three of the four temperate cities, but in only one of the three tropical cities. Results suggest that while vegetation phenology is consistently different between urban and rural areas, a uniform paradigm based on the explanatory variables in this study did not emerge. Although not testable here, it is likely that alterations to chilling requirements in temperate climates and humidity in tropical climates may also influence observed budburst differences. [ABSTRACT FROM AUTHOR]

By using the NCEP/NCAR reanalysis data, the Northern Hemisphere annular mode index (NAMI), China dust storm frequency data and China’s 160-station monthly precipitation data, the relationship between the previous winter (December–February) Northern Hemisphere annular mode (NAM) and the following spring (March–May) Asian atmospheric circulation is examined statistically in this study. Results demonstrate that the relationship between the spring Asian atmospheric circulation and the previous winter NAM is more significant on decadal time scales than on interannual time scales. There are significant negative correlations between the previous winter NAM and the spring temperature in what is almost a troposphere over Northwest China. There is a significant positive correlation between the winter NAMI and following spring geopotential height field over the Mongolian Plateau and Middle Siberia (MPMS) at the upper level. The positive correlation coefficients center moves to the south with the level from high to low. At lower level the high correlation coefficients center is located over the North China. There is a significant negative correlation between the winter NAMI and the surface horizontal wind intensity in the following spring for Northwest China on decadal timescales. The results suggest that a strong NAM in winter is followed by a negative temperature anomaly and a positive anomaly of the spring 500 hPa geopotential height over the MPMS, while at the same time the spring anomaly of the southeast wind is experienced in the surface layer in Northwest China, implying that the intensity of the northwest wind tends to weaken, and vice versa. This circulation pattern can affect the change of the spring dust storm frequency in Northwest China on decadal time scales. [ABSTRACT FROM AUTHOR]