scholarly journals Dry Tropical Nights and Wet Extreme Heat in Beijing: Atypical Configurations between High Temperature and Humidity

2014 ◽  
Vol 142 (5) ◽  
pp. 1792-1802 ◽  
Author(s):  
Ruidan Chen ◽  
Riyu Lu
Keyword(s):  
High Temperature ◽  
Solar Radiation ◽  
Large Scale ◽  
Longwave Radiation ◽  
Meteorological Conditions ◽  
Extreme Heat ◽  
Specific Humidity ◽  
Maximum Temperature ◽  
Dry Air ◽  
Radiation Cooling

Abstract Generally, tropical nights [TN; minimum temperature (Tmin) ≥25°C] occur under wet air conditions, while extreme heat [EH; maximum temperature (Tmax) ≥35°C] occurs under dry air conditions. This can be explained by higher humidity favoring TN through reducing longwave radiation cooling, and lower humidity favoring EH through enhancing solar radiation at the surface. The present study focuses on the atypical phenomena of dry TN (30% of all TN days) and wet EH (20% of all EH days) in Beijing during July and August, 1979–2008. It was found that meteorological conditions, including large-scale circulations and specific humidity, exhibit a resemblance between typical (wet TN and dry EH) and atypical (dry TN and wet EH) cases. That is, the meteorological anomalies for dry TN are similar to those for dry EH, and the anomalies for wet EH are similar to those for wet TN. For instance, descending anomalies, which lead to lower humidity and are thus associated with dry EH, appear for more than 70% of dry TN cases. In addition, the persistence of high temperature from day to night, and from night to day, also contribute significantly to dry TN and wet EH, respectively. About 50% of dry TN days and about 70% of wet EH days are preceded by EH and TN, respectively. It can be concluded from these results that both meteorological conditions and temperature persistence contribute greatly to dry TN and wet EH.

scholarly journals The dramatic retreat of Mount Kenya’s glaciers between 1963 and 1987: greenhouse forcing

1992 ◽  
Vol 16 ◽  
pp. 127-133 ◽  
Author(s):  
Stefan Hastenrath ◽  
Phillip D. Kruss
Keyword(s):  
Heat Transfer ◽  
Solar Radiation ◽  
Latent Heat ◽  
Greenhouse Effect ◽  
Longwave Radiation ◽  
Atmospheric Composition ◽  
Specific Humidity ◽  
Sensitivity Analyses ◽  
Sensible Heat ◽  
Indirect Forcing

The retreat of the glaciers on Mount Kenya is quantitatively well documented for the intervals 1899–1963 and 1963–1987. The ice recession between 1899 and 1963 was strongly dependent on solar radiation geometry. By contrast, the ice thinning between 1963 and 1987 amounted to about 15 m for all glaciers regardless of topographic location. This suggests that climatic forcings other than solar radiation have become more prominent. Sensitivity analyses indicate that the energy supply of about 5 W m−2, required to produce the observed ice thinning through melting, can be accounted for by a combination of climatic forcings. The direct effect of changing atmospheric composition (“greenhouse effect”) on the net longwave radiation could have contributed less than 1 W m−2. A warming of 0.0 to 0.2°C would translate into an additional downward-directed sensible heat transfer of 0.0 to 1.4 W m−2. A 0.1 to 0.2 g kg−1 increase in specific humidity would, through savings in the latent heat transfer, contribute 2 to 4 W m−2. Long-term station records show little warming trend for East Africa itself. However, mid-tropospheric specific humidity trends of about 0.6 g kg−1 over the past two decades in the equatorial belt have been reported in the literature, and considered to be consequences of “global warming” and the “greenhouse effect”. Viewed in perspective, the ice wastage on Mount Kenya between 1963 and 1987 appears to have been driven primarily by three climatic forcings, conceivably all steered by the “greenhouse effect”: a direct forcing through the net longwave radiation; an indirect forcing through warming and therefore enhanced sensible heat transfer; and another indirect forcing through warming (not necessarily in the region itself), leading to increased (advected) atmospheric moisture, and hence to reduced latent heat transfer, this last line of control being the most important.

scholarly journals The dramatic retreat of Mount Kenya’s glaciers between 1963 and 1987: greenhouse forcing

1992 ◽  
Vol 16 ◽  
pp. 127-133 ◽  
Author(s):  
Stefan Hastenrath ◽  
Phillip D. Kruss
Keyword(s):  
Heat Transfer ◽  
Solar Radiation ◽  
Latent Heat ◽  
Greenhouse Effect ◽  
Longwave Radiation ◽  
Atmospheric Composition ◽  
Specific Humidity ◽  
Sensitivity Analyses ◽  
Sensible Heat ◽  
Indirect Forcing

The retreat of the glaciers on Mount Kenya is quantitatively well documented for the intervals 1899–1963 and 1963–1987. The ice recession between 1899 and 1963 was strongly dependent on solar radiation geometry. By contrast, the ice thinning between 1963 and 1987 amounted to about 15 m for all glaciers regardless of topographic location. This suggests that climatic forcings other than solar radiation have become more prominent.Sensitivity analyses indicate that the energy supply of about 5 W m−2, required to produce the observed ice thinning through melting, can be accounted for by a combination of climatic forcings. The direct effect of changing atmospheric composition (“greenhouse effect”) on the net longwave radiation could have contributed less than 1 W m−2. A warming of 0.0 to 0.2°C would translate into an additional downward-directed sensible heat transfer of 0.0 to 1.4 W m−2. A 0.1 to 0.2 g kg−1 increase in specific humidity would, through savings in the latent heat transfer, contribute 2 to 4 W m−2.Long-term station records show little warming trend for East Africa itself. However, mid-tropospheric specific humidity trends of about 0.6 g kg−1 over the past two decades in the equatorial belt have been reported in the literature, and considered to be consequences of “global warming” and the “greenhouse effect”.Viewed in perspective, the ice wastage on Mount Kenya between 1963 and 1987 appears to have been driven primarily by three climatic forcings, conceivably all steered by the “greenhouse effect”: a direct forcing through the net longwave radiation; an indirect forcing through warming and therefore enhanced sensible heat transfer; and another indirect forcing through warming (not necessarily in the region itself), leading to increased (advected) atmospheric moisture, and hence to reduced latent heat transfer, this last line of control being the most important.

scholarly journals Recent Changes in U.S. Regional Heat Wave Characteristics in Observations and Reanalyses

2017 ◽  
Vol 56 (9) ◽  
pp. 2621-2636 ◽  
Author(s):  
J. T. Schoof ◽  
T. W. Ford ◽  
S. C. Pryor
Keyword(s):  
High Temperature ◽  
Heat Wave ◽  
Extreme Heat ◽  
Specific Humidity ◽  
Equivalent Temperature ◽  
Northern Plains ◽  
Wave Characteristics ◽  
Extreme Heat Events ◽  
Temperature And Humidity ◽  
Heat Events

AbstractHumidity is a key determinant of heat wave impacts, but studies investigating changes in extreme heat events have not differentiated between events characterized by high temperatures and those characterized by simultaneously elevated temperature and humidity. The authors present a framework, using air temperature (T) and equivalent temperature (TE; a measure combining temperature and specific humidity), to examine changes in local percentile-based extreme heat events characterized by high temperature (T only) and those with high temperature and humidity (T-and-TE events). Application to one observational dataset (PRISM), four reanalysis products (1981–2015), and seven U.S. regions reveals widespread changes in heat wave characteristics over the 35-yr period. Agreement among the datasets employed on several heat wave metrics suggests that many of the findings are robust. With the exception of the northern plains region, all regions experienced increases in both T-only and T-and-TE heat wave day (HWD) frequency in each of the reanalyses. In the northern plains, all datasets have negative trends in T-only HWD frequency and positive trends in T-and-TE HWD frequency. Trends in HWD frequency were generally accompanied by changes in the spatial footprint in heat wave conditions. Temperature has increased significantly during T-only HWDs in the western regions, while increases in TE during T-and-TE HWDs have occurred in the central United States and Northeast region. These findings suggest that equivalent temperature provides an alternative perspective on the evolution of regional heat wave climatology. Studies considering changes in regional heat wave impacts should carefully consider the role of atmospheric moisture.

Precipitation–Radiation–Circulation Feedback Processes Associated with Structural Changes of the ITCZ in a Warming Climate during 1980–2014: An Observational Portrayal

2020 ◽  
Vol 33 (20) ◽  
pp. 8737-8749 ◽  
Author(s):  
William K. M. Lau ◽  
Weichen Tao
Keyword(s):  
Relative Humidity ◽  
Large Scale ◽  
Structural Changes ◽  
Climate Model ◽  
Longwave Radiation ◽  
Hadley Circulation ◽  
Specific Humidity ◽  
Necessary Condition ◽  
Multiple Sources

AbstractIn this study, long-term structural changes in the intertropical convergence zone (ITCZ) and associated precipitation–radiation–circulation feedback processes are examined using multiple sources of reanalysis data for temperature, winds, moisture, and observed precipitation and outgoing longwave radiation (OLR) during 1980–2014. Consistent with CMIP5 climate model projections of the “deep tropical squeeze” under greenhouse warming, this period witnessed a warming and wetting (increased specific humidity) global trend, characterized by a narrowing of the ITCZ core with increased precipitation, coupled to widespread tropospheric drying (deficient relative humidity), increased OLR in the subtropics and midlatitudes, a widening of the descending branches of the Hadley circulation, and a poleward shift of the jet streams in both hemispheres. The widespread tropospheric drying stems from 1) a faster rate of increased saturated water vapor with warming, relative to the increase in ambient moisture due to convective and large-scale transport, and 2) enhanced anomalous subsidence, and low-level moisture divergence in the subtropics and midlatitudes. The long-term trend in enhanced precipitation (latent heating) in the ITCZ core region is strongly coupled to increasing OLR (radiative cooling to space) in the expanding dry zones, particularly over land regions in the subtropics and midlatitudes, arguably as a necessary condition for global thermodynamic energy balance. Analyses of the trend patterns in vertical profiles of p velocity, temperature, and relative humidity with respect to ITCZ precipitation rate and OLR reveal that the contrast between the wet and dry regions in the troposphere has been increasing globally, with the ITCZ core getting wetter and contracting, while the marginal convective and dry zones are getting drier and expanding.

scholarly journals Recent trends in climate variability at the local scale using 40 years of observations: the case of the Paris region of France

2019 ◽  
Vol 19 (20) ◽  
pp. 13129-13155 ◽  
Author(s):  
Justine Ringard ◽  
Marjolaine Chiriaco ◽  
Sophie Bastin ◽  
Florence Habets
Keyword(s):  
Global Warming ◽  
Large Scale ◽  
Climate Models ◽  
Specific Humidity ◽  
Maximum Temperature ◽  
Strong Increase ◽  
Large Scale Circulation ◽  
Surface Atmosphere ◽  
Paris Region ◽  
Local Variability

Abstract. For several years, global warming has been unequivocal, leading to climate change at global, regional and local scales. A good understanding of climate characteristics and local variability is important for adaptation and response. Indeed, the contribution of local processes and their understanding in the context of warming are still very little studied and poorly represented in climate models. Improving the knowledge of surface–atmosphere feedback effects at local scales is therefore important for future projections. Using observed data in the Paris region from 1979 to 2017, this study characterizes the changes observed over the last 40 years for six climatic parameters (e.g. mean, maximum and minimum air temperature at 2 m, 2 m relative and specific humidities and precipitation) at the annual and seasonal scales and in summer, regardless of large-scale circulation, with an attribution of which part of the change is linked to large-scale circulation or thermodynamic. The results show that some trends differ from the ones observed at the regional or global scale. Indeed, in the Paris region, the maximum temperature increases faster than does the minimum temperature. The most significant trends are observed in spring and in summer, with a strong increase in temperature and a very strong decrease in relative humidity, while specific humidity and precipitation show no significant trends. The summer trends can be explained more precisely using large-scale circulation, especially regarding the evolution of the precipitation and specific humidity. The analysis indicates the important role of surface–atmosphere feedback in local variability and that this feedback is amplified or inhibited in a context of global warming, especially in an urban environment.

scholarly journals Evolution of the Circulation Anomalies and the Quasi-Biweekly Oscillations Associated with Extreme Heat Events in Southern China

2016 ◽  
Vol 29 (19) ◽  
pp. 6909-6921 ◽  
Author(s):  
Ruidan Chen ◽  
Zhiping Wen ◽  
Riyu Lu
Keyword(s):  
High Temperature ◽  
Southern China ◽  
Circulation Pattern ◽  
The Philippines ◽  
Extreme Heat ◽  
Maximum Temperature ◽  
Daily Maximum Temperature ◽  
Daily Maximum ◽  
The North ◽  
Circulation Anomalies

Abstract Southern China, located in the tropical–subtropical East Asian monsoonal region, presents a unique anticyclonic–cyclonic circulation pattern during extreme heat (EH), obviously different from the typical anticyclone responsible for EH in many other regions. Associated with the evolution of EH in southern China, the anticyclonic–cyclonic anomalies propagate northwestward over the Philippines and southern China. Before the EH onsets, the anticyclonic anomaly dominates southern China, resulting in stronger subsidence over southern China and stronger southerly (southwesterly) flow over the western (northern) margins of southern China. The southerly (southwesterly) flow transports more water vapor to the north of southern China, thus, together with the local stronger subsidence, resulting in drier air condition and accordingly favoring the occurrence of EH. Conversely, after the EH onsets, the cyclonic component approaches southern China and offsets the high temperature. The oscillations of temperature and circulation anomalies over southern China exhibit a periodicity of about 10 days and indicate the influence of a quasi-biweekly oscillation, which originates from the tropical western Pacific and propagates northwestward. Therefore, the 5–25-day-filtered data are extracted to further analyze the quasi-biweekly oscillation. It turns out that the evolution of the filtered circulation remarkably resembles the original anomalies with comparable amplitudes, indicating that the quasi-biweekly oscillation is critical for the occurrence of EH in southern China. The quasi-biweekly oscillation could explain more than 50% of the intraseasonal variance of daily maximum temperature Tmax and vorticity over southern China and 80% of the warming amplitude of EH onsets. The close relationship between the circulation of the quasi-biweekly oscillation and the EH occurrence indicates the possibility of medium-range forecasting for high temperature in southern China.

Development of a Profiled Multilayer Tube for High Temperature Solar Receivers and Heat Exchangers

2010 ◽  
Author(s):  
Jens Jedamski ◽  
Lars Amsbeck ◽  
Reiner Buck ◽  
Raphael Couturier ◽  
Peter Heller ◽  
...  
Keyword(s):  
Heat Transfer ◽  
High Temperature ◽  
Temperature Distribution ◽  
Solar Radiation ◽  
Maximum Temperature ◽  
Outer Side ◽  
Internal Stresses ◽  
Fluid Temperature ◽  
Test Loop ◽  
Nickel Based Alloy

In solar tower plants absorber tubes are the main components of various solar receivers, e.g. steam receivers, salt receivers, pressurized air receivers. The solar radiation on the absorber tube causes an inhomogeneous temperature distribution because most of the solar radiation along the tube circumference is one-sided. The resulting internal stresses of the tube and the maximum fluid temperature decrease the lifetime significantly. Within the projects SOLHYCO and FUTUR a profiled multilayer tube (PML) is currently under development in order to reduce this problem. It consists of three metallic layers: a high temperature nickel-based alloy at the outer side, a copper layer as intermediate layer and another high temperature nickel-based alloy at the inner side of the tube. The outer layer provides the structural strength while the copper is used to conduct the heat from the irradiated side to the opposite side. The inner layer protects the copper from corrosion and oxidation at high temperatures. In addition, a wire coil is inserted (profiled) to increase the heat transfer on the inside. The PML is manufactured in a hydro-forming process by deforming the tube composite with water under high pressure. To demonstrate the performance and to determine the heat transfer, the pressure loss and the temperature distribution, a test loop was built to simulate the different loads under laboratory conditions. The thermo hydraulic measurements and finite element calculations show that the temperature gradient and the maximum temperature can be reduced significantly. Based on these studies the advantages of the PML in comparison to common tubes will be presented as well as several possibilities for future improvements.

scholarly journals MetSim v2.0.0: A flexible and extensible framework for the estimation and disaggregation of meteorological data

2019 ◽  
Author(s):  
Andrew R. Bennett ◽  
Joseph J. Hamman ◽  
Bart Nijssen
Keyword(s):  
Meteorological Data ◽  
Longwave Radiation ◽  
Specific Humidity ◽  
Shortwave Radiation ◽  
Automated Testing ◽  
Maximum Temperature ◽  
Temperature And Precipitation ◽  
Spatially Distributed ◽  
Temporal Disaggregation ◽  
Meteorological Simulation

Abstract. MetSim is a freely available, open source Python based model for simulation and disaggregation of meteorological variables with applications in the environmental and Earth sciences. MetSim can be used to generate spatially distributed sub-daily timeseries of incoming shortwave radiation, outgoing longwave radiation, air pressure, specific humidity, relative humidity, vapor pressure, precipitation, and air temperature given daily timeseries of minimum temperature, maximum temperature, and precipitation. Based on previously developed algorithms, we demonstrate that MetSim is able to closely reproduce their results while providing a number of advantages and improvements. We implemented automated testing to decrease errors during development and to improve reproducibility, modularized the algorithms to allow for extensions and modifications, and implemented robust single and multi-node parallelism. We describe the overall architecture, algorithms, and capabilities of MetSim by describing its four major modules. These are split into a model driver, solar geometry module, meteorological simulation module, and temporal disaggregation module. We also describe the available options and parameters that MetSim exposes to its users and analyze MetSim's scalability for large datasets.

scholarly journals Large-Scale Synoptic Systems and Fog During the C-FOG Field Experiment

2021 ◽  
Author(s):  
Clive E. Dorman ◽  
Sebastian W. Hoch ◽  
Ismail Gultepe ◽  
Qing Wang ◽  
Ryan T. Yamaguchi ◽  
...  
Keyword(s):  
Large Scale ◽  
Longwave Radiation ◽  
Meteorological Conditions ◽  
Cloud Base ◽  
Atlantic Canada ◽  
The North ◽  
Coastal Fog ◽  
Surface Measurements ◽  
Avalon Peninsula ◽  
Cloud Base Height

AbstractThe goal of this work is to summarize synoptic meteorological conditions during the Coastal Fog (C-FOG) field project that took place onshore and offshore of the Avalon Peninsula, Newfoundland, from 25 August until 8 October 2018. Visibility was measured at three locations at the Ferryland supersite that are about 1 km from each other, and at two additional sites 66 and 76 km to the north. Supporting meteorological measurements included surface winds, air temperature, humidity, pressure, radiation, cloud-base height, and atmospheric thermodynamic profiles from radiosonde soundings. Statistics are presented for surface measurements during fog events including turbulence kinetic energy, net longwave radiation, visibility, and precipitation. Eleven fog events are observed at Ferryland. Each significant fog event is related to a large-scale cyclonic system. The longest fog event is due to interaction of a northern deep low and a tropical cyclone. Fog occurrence is also examined across Atlantic Canada by including Sable Island, Yarmouth, Halifax, and Sydney. It is concluded that at Ferryland, all significant fog events occur under a cyclonic system while at Sable Island all significant fog events occur under both cyclonic and anticyclonic systems. The fog-formation mechanism involves cloud lowering and stratus broadening or only stratus broadening for the cyclonic systems while for the anticyclonic systems it is stratus broadening or radiation. Although widely cited as the main cause of fog in Atlantic Canada, advection fog is not found to be the primary or sole fog type in the events examined.

scholarly journals Forewarned is Forearmed: Extended-Range Forecast Guidance of Recent Extreme Heat Events in Australia

2016 ◽  
Vol 31 (3) ◽  
pp. 697-711 ◽  
Author(s):  
D. Hudson ◽  
A. G. Marshall ◽  
O. Alves ◽  
G. Young ◽  
D. Jones ◽  
...  
Keyword(s):  
Large Scale ◽  
Heat Waves ◽  
Weather Forecast ◽  
Seasonal Prediction ◽  
Extreme Heat ◽  
Maximum Temperature ◽  
Extreme Heat Events ◽  
Extended Range ◽  
Heat Events ◽  
Forecast Guidance

Abstract There has been increasing demand in Australia for extended-range forecasts of extreme heat events. An assessment is made of the subseasonal experimental guidance provided by the Bureau of Meteorology’s seasonal prediction system, Predictive Ocean Atmosphere Model for Australia (POAMA, version 2), for the three most extreme heat events over Australia in 2013, which occurred in January, March, and September. The impacts of these events included devastating bushfires and damage to crops. The outlooks performed well for January and September, with forecasts indicating increased odds of top-decile maximum temperature over most affected areas at least one week in advance for the fortnightly averaged periods at the start of the heat waves and for forecasts of the months of January and September. The March event was more localized, affecting southern Australia. Although the anomalously high sea surface temperature around southern Australia in March (a potential source of predictability) was correctly forecast, the forecast of high temperatures over the mainland was restricted to the coastline. September was associated with strong forcing from some large-scale atmospheric climate drivers known to increase the chance of having more extreme temperatures over parts of Australia. POAMA-2 was able to forecast the sense of these drivers at least one week in advance, but their magnitude was weaker than observed. The reasonably good temperature forecasts for September are likely due to the model being able to forecast the important climate drivers and their teleconnection to Australian climate. This study adds to the growing evidence that there is significant potential to extend and augment traditional weather forecast guidance for extreme events to include longer-lead probabilistic information.

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