Average Specific Humidity Research Articles

Long-term exposure to summer specific humidity and cardiovascular disease hospitalizations in the US Medicare population

IntroductionMost climate-health studies focus on temperature; however, less is known about health effects of exposure to atmospheric moisture. Humid air limits sweat evaporation from the body and can in turn exert strain on the cardiovascular system. We evaluated associations of long-term exposure to summer specific humidity with cardiovascular disease (CVD), coronary heart disease (CHD) and cerebrovascular disease (CBV) hospitalization. MethodsWe built an open cohort consisting of ∼63 million fee-for-service Medicare beneficiaries, aged ≥65, living in the contiguous US (2000–2016). We assessed zip code level summer average specific humidity and specific humidity variability, based on daily estimates from the Gridded Surface Meteorological dataset (∼4km spatial resolution). To estimate associations of summer specific humidity with first CVD, CHD, and CBV hospitalization, we used Cox-equivalent Poisson models adjusted for individual and area-level socioeconomic status indicators, temperature, and winter specific humidity. ResultsHigher summer average specific humidity was associated with an increased risk of CVD, CHD, and CBV hospitalization. We found hazard ratios (HRs) of 1.07 (95%CI: 1.07, 1.08) for CVD hospitalization, 1.08 (95%CI: 1.08, 1.09) for CHD hospitalization, and 1.07 (95%CI: 1.07, 1.08) for CBV hospitalization per IQR increase (4.0 g of water vapor/kg of dry air) in summer average specific humidity. Associations of summer average specific humidity were strongest for beneficiaries eligible for Medicaid and for beneficiaries with an unknown or other race. Higher summer specific humidity variability was also associated with increased risk of CVD, CHD, and CBV hospitalization. Associations were not affected by adjustment for temperature and regions of the US, as well as exclusion of potentially prevalent cases. ConclusionLong-term exposure to higher summer average specific humidity and specific humidity variability were positively associated with CVD hospitalization. As global warming could increase humidity levels, our findings are important to assess potential health impacts of climate change.

Investigation of Thin-Layer Drying of Coffee Beans Using a Double-Condenser Compression Refrigeration System: Effects of Air Mass Flux, Specific Humidity and Drying Temperature

The drying process is the key to the quality of the coffee produced. The allowable moisture content of coffee beans is 12%. The air mass flux, specific humidity, and the drying temperature are varied using a bed dryer drying system combined with a double condenser refrigeration system. Robusta coffee beans are used in this research to obtain the characterization of coffee beans. The highest drying rate constant is obtained by 2.44 × 10-4 s-1 directly proportional to the increased air mass flux and drying air temperature, with a value of 1.701 kg/s m2 and 80 °C, but inversely proportional to the specific humidity, with a value of 7.01 g/kg d.a. The lowest activation energy value was 31.88 kJ/mol when the air mass flux was 1.701 kg/s m2, the drying air temperature was 80 °C, and the average specific humidity was 7.01 g/kg d.a. In this work, the developed correlation is proposed to practically predict the activation energy (EA) and the pre-exponential factor (A) with equation and respectively. Based on Ea and A correlation equation, it can be used for designing a bed dryer type coffee drying system for a larger scale.

Long-term exposure to specific humidity and cardiovascular disease hospitalizations in the US Medicare population

BACKGROUND AND AIM: Most studies that evaluate associations of weather on human health focus on temperature. Less is known about health effects of humidity. We evaluated associations of long-term exposure to specific humidity with cardiovascular disease (CVD), coronary heart disease (CHD) and cerebrovascular disease (CBV) hospitalization. METHODS: We constructed an open cohort consisting of all fee-for-service Medicare beneficiaries, aged ≥65, living in the contiguous US from 2000 through 2016 (~63 million individuals). We assessed zip code level annual (January-December), summer (June-August) and winter (December-February) average specific humidity and specific humidity variability (standard deviation) for each year, based on daily specific humidity estimates from the Gridded Surface Meteorological dataset (~4km spatial resolution). To estimate associations of specific humidity with first CVD, CHD and CBV hospitalization, we used Cox-equivalent Poisson models. RESULTS:After adjustment for individual and area-level indicators and temperature, higher annual and summer average specific humidity and lower winter average specific humidity were associated with an increased risk of CVD, CHD and CBV hospitalization. For summer average specific humidity, we found HRs of 1.07 (95%CI: 1.07, 1.08) for CVD hospitalization, 1.08 (95%CI: 1.08, 1.09) for CHD hospitalization and 1.07 (95%CI: 1.07, 1.08) for CBV hospitalization per IQR increase (4.0 g of water vapor/kg of dry air). Higher annual, summer and winter specific humidity variability were also associated with increased risk of CVD, CHD and CBV hospitalization. Associations of annual and summer average specific humidity were strongest for beneficiaries eligible for Medicaid and for beneficiaries with an unknown or other race. CONCLUSIONS:Among this cohort of US Medicare beneficiaries, higher annual and summer average specific humidity and higher annual, summer and winter specific humidity variability were positively associated with CVD, CHD, and CBV hospitalization. Associations were modified by race and Medicaid eligibility. KEYWORDS: humidity, cardiovascular diseases, climate

Trend analysis of tropospheric specific humidity over Iran during 1979–2016

In this study, the variation and trend of specific humidity (SH) of the troposphere (1,000–500 hPa) over Iran was analysed using the monthly European Center for Medium Range Weather Forecasting (ECMWF) Re‐Analysis Interim (ERA‐Interim) gridded data from January 1979 to December 2016. By using nonparametric modified Mann–Kendall test, the trend of values for each gridded point was tested in eight different atmospheric levels at 95% confidence level. The Sen's slope estimator test was used to estimate the change rate. The findings showed that the annual trend of SH is decreasing in most of Iran and is only increasing on the northern and southern coast of the country. The highest increasing trend of the SH is observed on the southern coast of Iran in 1,000 hPa. The regression line fitting on the standardized time series of Iran's area average SH showed that the highest decreasing rate occurred in the first layer (1,000–850 hPa) and only the third layer (600–500 hPa) has had a significant increase of SH trend over Iran. Area average annual anomaly of the tropospheric cross sections indicates that the studied period is divided into two periods: a wet period (1979–1998) and a dry period (1999–2016).

Anomalous holiday precipitation over southern China

Abstract. The Chinese Spring Festival (CSF, also known as the Chinese New Year or Lunar New Year) is the most important festival in China. Lunar New Year's Day (LNYD) is the first day of the Lunar New Year. Traditionally, the CSF holiday begins a couple of days before LNYD and ends on lantern day, lasting for approximately 2 weeks. In this paper, based on the long-term station observations from 1979 to 2012, the precipitation during the holiday over southern China (108–123° E and 21–33° N, 155 stations) tends to be lower than that before and after the holiday. The mean precipitation frequency anomaly from the fourth day to the sixth day after LNYD (i.e., days [+4, +6]) decreases by −7.4 %. Simultaneously, the daily precipitation amount experiences a reduction of −0.62 mm day−1 during days [+2, +5]. The holiday precipitation anomalies are strongly linked to the anomalies of relative humidity (ΔRH) and cloud cover. The station observations of the ΔRH show an evident decrease from day +2 to day +7, and a minimum appears on days [+4, +6], with a mean of −3.9 %. The ΔRH vertical profile displays significant drying below approximately 800 hPa. Between 800 and 1000 hPa, the mean ΔRH is −3.9 %. The observed station daytime low cloud cover (LCC) evidently decreases by −6.1 % during days [+4, +6]. Meanwhile, the ERA-Interim daily LCC also shows a comparable reduction of −5.0 %. The anomalous relative humidity is mainly caused by the decreased water vapor in the lower-middle troposphere. Evident negative specific humidity anomalies persist from day −3 to day +7 in the station observations. The average specific humidity anomaly for days [+4, +6] is −0.73 g kg−1. When the precipitation days are excluded, the anomaly remains significant at −0.46 g kg−1. A significant water vapor deficit is observed in the lower troposphere below 700 hPa. Between 800 and 1000 hPa, the mean specific humidity drops by −0.70 g kg−1. This drier lower-middle troposphere is due to anomalous northerly winds, which are closely related to the cyclonic circulation anomaly over the northwestern Pacific. The time-lag correlation demonstrates that approximately 1 week after a lower temperature occurs over eastern China, a stronger cyclone is observed over the western Pacific. The possible mechanism needs further clarification through elaborate observation and numerical modeling.

Establishment and Evaluation of the China Meteorological Assimilation Driving Datasets for the SWAT Model (CMADS)

We describe the construction of a very important forcing dataset of average daily surface climate over East Asia—the China Meteorological Assimilation Driving Datasets for the Soil and Water Assessment Tool model (CMADS). This dataset can either drive the SWAT model or other hydrologic models, such as the Variable Infiltration Capacity model (VIC), the Soil and Water Integrated Model (SWIM), etc. It contains several climatological elements—daily maximum temperature (°C), daily average temperature (°C), daily minimum temperature (°C), daily average relative humidity (%), daily average specific humidity (g/kg), daily average wind speed (m/s), daily 24 h cumulative precipitation (mm), daily mean surface pressure (HPa), daily average solar radiation (MJ/m2), soil temperature (K), and soil moisture (mm3/mm3). In order to suit the various resolutions required for research, four versions of the CMADS datasets were created—from CMADS V1.0 to CMADS V1.3. We have validated the source data of the CMADS datasets using 2421 automatic meteorological stations in China to confirm the accuracy of this dataset. We have also formatted the dataset so as to drive the SWAT model conveniently. This dataset may have applications in hydrological modelling, agriculture, coupled hydrological and meteorological modelling, and meteorological analysis.

Environmental Predictors of Seasonal Influenza Epidemics across Temperate and Tropical Climates

Human influenza infections exhibit a strong seasonal cycle in temperate regions. Recent laboratory and epidemiological evidence suggests that low specific humidity conditions facilitate the airborne survival and transmission of the influenza virus in temperate regions, resulting in annual winter epidemics. However, this relationship is unlikely to account for the epidemiology of influenza in tropical and subtropical regions where epidemics often occur during the rainy season or transmit year-round without a well-defined season. We assessed the role of specific humidity and other local climatic variables on influenza virus seasonality by modeling epidemiological and climatic information from 78 study sites sampled globally. We substantiated that there are two types of environmental conditions associated with seasonal influenza epidemics: “cold-dry” and “humid-rainy”. For sites where monthly average specific humidity or temperature decreases below thresholds of approximately 11–12 g/kg and 18–21°C during the year, influenza activity peaks during the cold-dry season (i.e., winter) when specific humidity and temperature are at minimal levels. For sites where specific humidity and temperature do not decrease below these thresholds, seasonal influenza activity is more likely to peak in months when average precipitation totals are maximal and greater than 150 mm per month. These findings provide a simple climate-based model rooted in empirical data that accounts for the diversity of seasonal influenza patterns observed across temperate, subtropical and tropical climates.

A calibrated advection‐aridity evaporation model requiring no humidity data

A modified advection‐aridity model was tested with 24 h averaged data from the First ISLSCP (International Satellite Land Surface Climatology Project) Field Experiment‐87 and the Cooperative Atmospheric‐Surface Exchange Study (CASES) ‐97 experiments. Two modifications were made. First, the need for humidity measurements in the “drying power” term of the equation was circumvented by assuming the daily average specific humidity for a 24 h day is equal to the specific humidity at the minimum temperature during the day. When compared to measured latent heat fluxes, this modification resulted in no deterioration in advection‐aridity estimates compared to versions using measured humidity. A second modification followed previous researchers by formulating the drying power in the Penman equation using Monin‐Obukhov similarity (MOS) theory. However, this version calibrated kB−1 (≡ln(zo/zov) by setting the Priestley‐Taylor evapotranspiration rate equal (on average) to the Penman evapotranspiration on several moist days and solving for the value of kB−1 as the only unknown. The calibration involved no latent heat flux measurements. The results suggest that the advection‐aridity model performs modestly better in the calibrated MOS version than with Penman's original wind function. Further investigation is recommended because MOS theory accounts for varying momentum roughness lengths, and the calibration was not done under ideal (well‐watered or nearly saturated) conditions that deteriorated the results somewhat with the CASES data set.

Tropospheric moisture and its relation with rainfall due to nor’westers in Bangladesh

Attempts have been made to compute the precipitable water content of the troposphere, weighted average water vapour and to correlate these parameters with different instability indices and also with the next 24-hr rainfall, next 24-hr maximum rainfall and next 24-hr country averaged rainfall in order to predicting rainfall due to nor’westers in Bangladesh. It has been found that the maximum number of nor’westers occur when the precipitable water is 25-45 mm hr-1 between 1000 and 500 hPa, the maximum frequency being 48 in the range of 35-45 mm hr-1. The spatial distribution of precipitable water indicates that the maximum precipitable water is concentrated over the area near the places of nor’westers. The specific humidity has been found to increase on the dates of occurrence of nor’westers in Bangladesh on most occasions. Maximum number of nor’westers occurs when the weighted average specific humidity between the surface (1000 hPa) and 500 hPa is 8-12 g kg-1, the maximum frequency being 43 in the range of 8-10 g kg-1. The study reveals that nor’westers have been found to occur near or at the eastern end of maximum weighted average specific humidity. It has also been found that nor’westers occur near the point of inter-section of the axes of moist and dry zones. A number of parameters of the troposphere over Dhaka at 0000 UTC on the dates of occurrence of nor’westers such as precipitable water (mm/hr), MSWI, SWI, SWI/TT, (q1000 – q850) weighted averaged specific humidity have statistically significant correlations with next 24-hour rainfall at Dhaka, next 24-hour maximum rainfall in Bangladesh and country averaged rainfall. The correlation co-efficients are relatively small and the standard errors of estimates are higher. The small correlation co-efficients are significant because of the large number of data.

Boundary layer humidity reconstruction for a semiarid location from tree ring cellulose δ18O

July–September boundary layer humidity has been reconstructed from the δ18O of cellulose in tree rings of Pinus arizonica growing at an elevation of 2300 m in the Santa Catalina Mountains north of Tucson, Arizona. The annual occurrence of morphological features in the tree rings, often called false rings, allowed accurate subdivision of the tree rings into premonsoon and monsoon growth. Highly significant correlations were found among the stable oxygen isotope time series of the wood produced during the North American Monsoon and 1953–2000 July–September average specific humidity (P < 0.0001) and relative humidity (P < 0.0001) derived from radiosonde data. The correlation coefficients were significant against data from both the Tucson surface (788 m; approximately 922 hPa) and 850 hPa pressure levels, suggesting that the δ18O time series can be interpreted as a proxy for mean seasonal boundary layer humidity. Twentieth century July–September reconstructions of specific humidity and relative humidity are presented. There are no long‐term trends in the twentieth century reconstructions of boundary layer humidity at this site.

Water‐vapour flux and flux‐divergence over Southern England: Summer 1954

AbstractAverage zonal (eastward) and meridional (northward) transfers of water vapour for the period June‐August 1954 are computed at four aerological stations in southern England ‐ Liverpool, Hemsby, Crawley and Camborne‐at levels corresponding to the earth's surface, 950, 900, 850, 800, 750, 650, 550, 450, and 350 mb.In the zonal direction average transfers are eastwards and reach a maximum of 400–500 g (cm 100 mb sec)−1 below 900 mb. In the meridional direction both northward and southward transfers occur and their vertical distribution varies from station to station. Largest meridional transfers are of the order of 100 g (cm 100 mb sec)−1 and normally occur below 800 mb. Both zonal and meridional transfers become small near 350 mb. Vertically integrated eastward and northward transfers are respectively: Liverpool 1461, ‐13; Hemsby 1541, 226; Crawley 1701, 132; Camborne 1781, ‐42 g (cm sec)−1..Average zonal eddy‐transfers are normally eastward and amount to only a small percentage of the total zonal transfer. Average meridional eddy‐transfers are northward, amount to a large percentage of the total meridional transfer and in some cases are oppositely directed. Vertically integrated eastward and northward eddy‐transfers are respectively: Liverpool 63, 73; Hemsby 81, 58; Crawley 97, 27; Camborne 113, 125 g (cm sec)−1. Although directed roughly from high to low values of average specific humidity, average eddy‐transfer vectors at a given (geometric or pressure) level bear little quantitative relation to average (horizontal or isobaric) specific humidity gradients at the same level.Assuming the above transfers to vary linearly between stations, computation of the net horizontal outflow of water vapour from the region shows marked convergence of water vapour from the surface to 850 mb with divergence above this. For the three months' period this amounts to a net inflow of 31 g cm−2 at low levels and a net outflow of 23 g cm−2 at higher levels. Increase in storage amounts to approximately 1 g cm−2, thus leaving a surplus of precipitation over evaporation of approximately 7 g cm−2. Estimation of precipitation from isohyetal charts and evapotranspiration by empirical methods yields a corresponding surplus of 6 g cm−2..Computation of the large‐scale vertical transfer of water vapour (using instantaneous kinematically‐computed vertical velocities) at 900, 800, 700 and 600 mb showed that at these levels large‐scale vertical eddy‐transfer of water vapour is negligibly small. Using mean vertical velocities and specific humidity averaged over the area at 950, 850, 750, 650, 550 and 450 mb, computations yield large‐scale upward transfers of water vapour for the three months' period amounting to 17, 23, 13, 6, 2, 0 g cm−2 respectively at the above levels. This flux is shown to be inadequate for water‐balance requirements and it is concluded that a considerable part of the upward transfer is carried by turbulent and convective systems of essentially smaller scales.

Fuel Testing in Gas‐Turbines

THE performance of a gas turbine fuel can be estimated most conveniently by using a single combustion chamber test unit. Such fuel testing has often shown a lack of repeatability that is difficult to ascribe to normal experimental errors only. In reviewing possible sources of error, the uncontrolled variable of atmospheric humidity has been considered. From past records the average specific humidity in the British Isles is 0·006 lb. water per lb. of dry air while the maximum on any day is unlikely to exceed 0·020 lb. water per lb. of dry air.