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News Article | May 11, 2017
Site: www.eurekalert.org

Reduced dust slows winds, increases air stagnation over cities like Beijing; implications for US, other cities as well Man-made pollution in eastern China's cities worsens when less dust blows in from the Gobi Desert, according to a new study published May 11 in Nature Communications. Yes, you read that correctly: When less natural dust blows in, the air quality for millions of people worsens. That's because dust plays an important role in determining the air temperatures and thereby promoting winds to blow away man-made pollution. Less dust means the air stagnates, with man-made pollution becoming more concentrated and sticking around longer. The scientists found that reduced dust causes a 13 percent increase in man-made pollution over eastern China during the winter. Researchers say the broader question of how natural dust and man-made pollution interact is an important one for people across the globe, not just China. Many of the same forces that ease or worsen pollution in China are at play in many areas around the globe, including several cities in the United States. The paradoxical finding -- that more natural dust in the air improves air quality -- comes from a team of researchers from the Department of Energy's Pacific Northwest National Laboratory and Scripps Institution of Oceanography at the University of California at San Diego. Post-doctoral researcher Yang Yang of PNNL is first author of the paper, and Lynn Russell of Scripps is the corresponding author. In computer models together with historical data, the team found that reduced natural dust transported from the Gobi Desert in central and northern China translates to increased man-made air pollution in highly populated eastern China. The reason is that natural dust particles in the air help deflect sunlight. Fewer dust particles translates to a warmer-than-usual land surface and cooler-than-usual water. That reduces the temperature differential in winter between sea and the land, resulting in weaker winds -- and increased air stagnation. As a result, during the winter monsoon season, eastern China experiences weaker winds when there's less natural dust in the air. It's nothing a person would notice -- a reduction barely more than one-tenth of one mile per hour -- but on a large scale over an entire region, such a seemingly minor change has a profound effect on climate and air quality. "This is one of the first times we've really looked at the interactions between natural dust, wind, and anthropogenic pollution," said Yang. "It turns out that dust plays an important role in determining the quality of the air for many people in eastern China." The modeling results match observational data from dozen of sites in eastern China. The team found that two to three days after winds had brought dust into the region from western China, the air was cleaner than before the dust arrived. The researchers say man-made pollution is still the core of air pollution in cities like Beijing in eastern China but that it's important to understand the role of natural dust particles. In addition to authors from Scripps and PNNL, scientists from Nanjing University of Information Science and Technology and the Chinese Academy of Meteorological Sciences contributed to the study. Work was funded by the National Science Foundation and the Department of Energy Office of Science. Some of the research was performed at the National Energy Research Scientific Computing Center, an Office of Science national user facility on the campus of DOE's Lawrence Berkeley National Laboratory. Yang Yang, Lynn M. Russell, Sijia Lou, Hong Liao, Jianping Guo, Ying Liu, Balwinder Singh and Steven J. Ghan, Dust-wind interactions can intensify aerosol pollution over eastern China, Nature Communications, May 11, 2017, http://dx. .

News Article | April 26, 2017
Site: www.newscientist.com

Typhoon Haiyan was already one of the strongest tropical storms on record. Now it has another claim to fame. Analysis of satellite data has revealed that the storm, which hit the Philippines in 2013, hosted a spectacular lightning show in its innermost core – something not seen in recorded storms of similar intensity. Haiyan was found to have lightning at its core for 49 per cent of its life between 3 and 11 November that year, when it killed some 6300 people and wreaked huge damage to property and infrastructure. By comparison, hurricanes Rita and Katrina had lightning at their cores for just 5 and 3 per cent of their existence, respectively. “Lightning is usually infrequent in the inner core [of a storm],” says Wenjuan Zhang at the Chinese Academy of Meteorological Sciences in Beijing. “Normally, lightning is found at the periphery of storms.” Zheng presented her findings on 24 April in Vienna, Austria, at the annual meeting of the European Geosciences Union. They arise from an analysis of data on the lightning from space satellites, as well as from 70 stations on the ground that comprise the World Wide Lightning Location Network. She added that tracking lightning from space may turn out to be another way to monitor and predict the intensity of storms. “Lightning may be a proxy for intense convection,” she says. But more research is needed to see if this is really the case. Zhang’s analysis showed that the core lightning occurred in three stages of Haiyan’s life: as it intensified rapidly in the west Pacific; at the point of its maximum intensity; and towards the end of its life, as it veered away from the Philippines towards the Asian mainland. She also found that the conditions where Haiyan formed were perfect for lightning to evolve, with unusually warm seas, high humidity and low crosswinds. These factors enabled the formation of high “tower” clouds, which accumulate positive and negative ions at different heights – almost like an enormous battery. With large areas of opposite charge building up within clouds, lightning strikes between clouds and down to the ground were abundant. The other striking thing, says Zhang, was that the lightning in the first two phases coincided with a storm formation that remained almost perfectly symmetrical when viewed from above. This may have been a further factor in focusing the lightning in the eye of the storm, she says, though it’s not yet clear if this was the case. Only in the final phase did the symmetry disappear. But the core lightning re-emerged as Haiyan veered north, possibly because of changes in the interaction of crosswinds and storm movement.

News Article | May 3, 2017
Site: www.eurekalert.org

Studies of raindrop size distribution (DSD) over different regions help to advance our understanding of DSD characteristics and provide observational facts regarding the development and evaluation of microphysical parameterization schemes in numerical models over different regions in the future. Liping LIU, from the Chinese Academy of Meteorological Sciences, and his colleagues, analyzed DSD data over the Tibetan Plateau (Nagqu) and southern China (Yangjiang) from April to August 2014, collected by HSC-PS32 disdrometers; in particular, the raindrop spectra and characteristics of parameter variations with rainfall rate for stratiform and convective precipitation, and the relationships between reflectivity factor and rainfall rate (Z-R relationships). The results are published in Advances in Atmospheric Sciences, and the paper is featured on the cover of Volume 34, Issue 6. The results indicate that the raindrop number concentration for convective precipitation over Tibet is much lower than that in southern China; and for larger raindrops, the condition is similar for stratiform precipitation. The rainfall rate over Tibet, with the same radar reflectivity, is much heavier than that over southern China. In terms of the radar QPE (quantitative precipitation estimation) equation, Z = aRb, the coefficient a over the Tibetan Plateau is smaller than that over southern China, while the value of b is higher, especially for convective precipitation.

Human life and the entire ecosystem of South East Asia depend upon the monsoon climate and its predictability. More than 40% of the earths population lives in this region. Droughts and floods associated with the variability of rainfall frequently cause serious damage to ecosystems in these regions and, more importantly, injury and loss of human life. The headwater areas of seven major rivers in SE Asia, i.e. Yellow River, Yangtze, Mekong, Salween, Irrawaddy, Brahmaputra and Ganges, are located in the Tibetan Plateau. Estimates of the Plateau water balance rely on sparse and scarce observations that cannot provide the required accuracy, spatial density and temporal frequency. Fully integrated use of satellite and ground observations is necessary to support water resources management in SE Asia and to clarify the roles of the interactions between the land surface and the atmosphere over the Tibetan Plateau in the Asian monsoon system. The goal of this project is to: 1. Construct out of existing ground measurements and current / future satellites an observing system to determine and monitor the water yield of the Plateau, i.e. how much water is finally going into the seven major rivers of SE Asia; this requires estimating snowfall, rainfall, evapotranspiration and changes in soil moisture; 2. Monitor the evolution of snow, vegetation cover, surface wetness and surface fluxes and analyze the linkage with convective activity, (extreme) precipitation events and the Asian Monsoon; this aims at using monitoring of snow, vegetation and surface fluxes as a precursor of intense precipitation towards improving forecasts of (extreme) precipitations in SE Asia. A series of international efforts initiated in 1996 with the GAME-Tibet project. The effort described in this proposal builds upon 10 years of experimental and modeling research and the consortium includes many key-players and pioneers of this long term research initiative.

News Article | December 6, 2016
Site: www.eurekalert.org

Dust storms have important climatic and environmental effect. Particularly, dust containing nutrients (nitrogen, phosphorus, and iron, etc.) could exert a significant influence on the biogeochemical cycle in downwind sea regions, stimulate marine biological productivity, and reduce atmospheric CO2 concentrations ("iron hypothesis" proposed in late 1980s). Since "iron hypothesis", scientists begun to pay attention to the impacts of atmospheric deposition on marine biogeochemical cycle. However, few studies have examined the direct link between natural dust events and marine biological productivity. In recent years, a series studies of Dr. TAN Saichun and Prof. SHI Guangyu from the Institute of Atmospheric Physics of the Chinese Academy of Sciences and their co-authors from Ocean University of China and Chinese Academy of Meteorological Sciences found that significant correlations were observed between East Asian dust events and chlorophyll a concentration not only in the open ocean of North Pacific Ocean, but also in the Chinese marginal seas. In addition to long-term statistics analysis, dust storm cases studies also found that phytoplankton growth in the Yellow Sea was related to dust deposition, and peak chlorophyll a concentration in dust years was above 40% higher than that in non-dust years. Those studies suggested the effects of dust fertilization on marine biological productivity. Recently, the team further investigated the transport process of East Asian dust events and quantitatively estimated the contribution of dust deposition to phytoplankton growth. They found that the combination of satellite-observed column and vertical properties of aerosol were able to show the transport of dust storms from the source regions to the research seas (Chinese marginal seas and southern North Pacific) and reduce the uncertainty of the identification of dust affecting the seas. The contribution of dust deposition to marine biological productivity was estimated from model simulated dust deposition flux. Results showed that dust containing iron was the most important factor affecting phytoplankton growth and the deposition of iron via severe dust storms satisfied the increase in demand required for phytoplankton growth (115-291%), followed by nitrogen (it accounted for up to 1.7-4.0%), and phosphorus was the smallest one (it accounted for up to 0.2-0.5%).

News Article | February 15, 2017
Site: www.eurekalert.org

Global warming increases the water holding capacity of the atmosphere and thus precipitation characteristics are expected to change. Changing precipitation characteristics directly affect society through their impacts on drought and floods, hydro-dams and urban drainage systems. An understanding of the changes in precipitation characteristics is not only important for climate research but also of great significant merit in the management of water resources and agricultural activities. "To address climate change, detection and attribution studies of precipitation are essential. Nonetheless, the detection of regional precipitation change has been a challenge, especially at regional scale. Whether anthropogenic climate change is manifested through a detectable effect on East Asian precipitation remains unknown." Said the first author Dr. Shuangmei Ma of a recent study published in Journal of Climate. Ma currently works at Chinese Academy of Meteorological Sciences. Supervised by her Ph.D advisor, Prof. Tianjun Zhou from the Institute of Atmospheric Physics/Chinese Academy of Sciences, her Ph. D research focused on detection and attribution of anthropogenic precipitation change over China. Their recently published work was the first attempt to investigate the changes in the distribution of the daily precipitation amount over China during the last five decades using observation data sets. They and their American and European collaborators applied the optimal fingerprinting detection and attribution method to assess the anthropogenic contribution to precipitation changes, based on the outputs of the CMIP5 models. "The results show that anthropogenic forcing has had a detectable and attributable in?uence on the distribution of daily precipitation amounts over eastern China (EC) during the second half of the twentieth century." Prof. Tianjun Zhou, who is the corresponding author of the paper, summarized their findings. "We have also found evidences suggesting that the observed shift from weak precipitation to intense precipitation is primarily due to the contribution of greenhouse gas (GHG) forcing, with anthropogenic aerosol (AA) forcing offsetting some of the effects of the GHG forcing." Under GHG-induced warming, increased atmospheric precipitable water and enhanced land-sea thermal contrast cause the water vapor transport to EC from the adjacent oceans via southerly and midlatitude westerly winds to strengthen, thereby favoring heavier precipitation over EC. However, the countering effects of surface cooling induced by anthropogenic aerosols meant that some of this enhanced transport is cancelled out by AA forcing. "We should also note that while the GHG forcing to the observed precipitation change is attributable and detectable, the signal of AA forcing is not as robust as GHG due to the limitations of aerosol schemes used in the current state of the art models." Zhou is hopeful that "the new models used in the Global Monsoons Modeling Inter-comparison Project (GMMIP) for the 6th Coupled Model Inter-comparison Project (CMIP6) would have improvement in this regard".

Zhang R.,Chinese Academy of Meteorological Sciences | Zuo Z.,Chinese Academy of Meteorological Sciences
Journal of Climate | Year: 2011

Numerous studies have been conducted on the impact of soil moisture on the climate, but few studies have attempted to diagnose the linkage between soil moisture and climate variability using observational data. Here, using both observed and reanalysis data, the spring (April-May) soil moisture is found to have a significant impact on the summer (June-August) monsoon circulation over East Asia and precipitation in east China by changing surface thermal conditions. In particular, the spring soil moisture over a vast region from the lower and middle reaches of the Yangtze River valley to north China (the YRNC region) is significantly correlated to the summer precipitation in east China. When the YRNC region has a wetter soil in spring, northeast China and the lower and middle reaches of the Yangtze River valley would have abnormally higher precipitation in summer, while the region south of the Yangtze River valley would have abnormally lower precipitation. An analysis of the physical processes linking the spring soil moisture to the summer precipitation indicates that the soil moisture anomaly across the YRNC region has a major impact on the surface energy balance. Abnormally wet soil would increase surface evaporation and hence decrease surface air temperature (T a). The reduced T a in late spring would narrow the land-sea temperature difference, resulting in the weakened East Asian monsoon in an abnormally strengthened western Pacific subtropical high that is also located farther south than its normal position. This would then enhance precipitation in the Yangtze River valley. Conversely, the abnormally weakened East Asian summer monsoon allows the western Pacific subtropical high to wander to south of the Yangtze River Valley, resulting in an abnormally reduced precipitation in the southern part of the country in east China. © 2011 American Meteorological Society.

Wang Y.Q.,Chinese Academy of Meteorological Sciences
Meteorological Applications | Year: 2014

MeteoInfo is a suite of software tools which has been developed for meteorological data visualization and analysis. It includes a .NET class library for software developers and a desktop application for end users. MeteoInfo also supports several basic GIS functions and can read widely several used meteorological data formats such as NetCDF and GRIB. Complex meteorological analyses of grid and station data can be processed using provided data models. The class library can be conveniently used to develop software routines for manipulating spatial and meteorological data. The desktop application has a user friendly GUI and is a powerful tool to view and examine meteorological data sets. MeteoInfo can also be run automatically using scripting with the IronPython language. © 2012 Royal Meteorological Society.

Chinese Academy of Meteorological Sciences | Date: 2012-03-15

A total-sky lightning event observation system and method may include a photographing device, a housing, a temperature control device, a light shielding device, a control module, a power supply module, a corona current sensor, a data acquisition device, a GPS antenna, a GPS timing module and a processing unit. The photographing device can capture total-sky digital images and transmit the images directly to the processing unit. The processing unit consecutively acquire corona current via the data acquisition device and judges whether there exists thunderstorm activity within the observed range; if there exists thunderstorm activity, the light shielding device is opened so as to enter a lightning observation mode, and the light shielding device is closed after the observation is finished so as to protect the photographing device in non-thunderstorm weather.

News Article | September 14, 2016
Site: www.nature.com

As the climate warms, tiny particles suspended in the atmosphere may have a greater effect than greenhouse gases on increasing the frequency of extreme rain and snowfall. Greenhouse gases and atmospheric aerosols both drive extreme precipitation, which is expected to increase with climate change. To tease apart the climate effects, Zhili Wang of the Chinese Academy of Meteorological Sciences in Beijing and his colleagues used a global climate model to simulate scenarios with different levels of greenhouse-gas emissions. They predict that, by the end of the century, aerosols will be two to four times more important than greenhouse gases in boosting precipitation extremes worldwide. Reducing aerosol emissions could help people to alter future climate-change impacts.

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