Andrelative Humidity Research Articles

A new smog chamber system for atmospheric multiphase chemistry study: design and characterization

Abstract. Multiphase chemistry is an important pathway for the formation of secondary organic aerosols (SOAs) in the atmosphere. In this study, an indoor 2 m3 Teflon chamber system (Aerosol multIphase chemistry Research chamber, AIR) was developed and characterized to specifically simulate atmospheric multiphase chemistry processes. The temperature and humidity controls, diurnal variation simulation, and seed particle generation unit in this chamber system were designed to meet the needs of simulating multiphase atmospheric chemical reactions. The AIR chamber is able to accurately control temperature (2.5–31 ± 0.15 ∘C) and relative humidity (RH <2 %–>95 % ± 0.75 %) over a relatively broad range. In addition, an RH regulation module inside the chamber was designed to simulate the diurnal variation of ambient atmospheric RH. The aerosol generation unit is able to generate pre-deliquescent seed particles with an organic coating across a wide range of phase states or morphologies. The organic coating thickness of the aerosols within the chamber can be precisely controlled through adjusting the condensation temperature, further helping to elucidate the roles of seed particles in multiphase chemical reactions. The inner walls of the AIR chamber are passivated to reduce the wall loss rates of reactive gases. Yield experiments of α-pinene ozonolysis with and without seed particles combined with a box model simulation demonstrate the high-quality performance of secondary aerosol formation simulation using the AIR chamber.

AUTOMATED TEMPERATUREAND HUMIDITY CONTROL AND MONITORING SYSTEM FOR IMPROVING THE PERFORMANCE IN DRYING SYSTEM

Temperature and relative humidity are the key control parameters in drying processes for preserving and improving food quality. To achieve this goal, an automatic control system has been designed and built to provide adequate heat and drying streams according to the ambient requirements of various climatic zones and the kind of dried product. The control system combined with sensors allows the temperature and humidity of the drying chamber to be adjusted online by predetermined parameters. When there is little or no radiation present or when rapid drying rates are required, the heated air stream may be produced utilizing an electric motor fan in addition to an electrical backup heater. The fan automatically modifies its speed using the Pulse Width Modulationtechniquefor energy efficiency depending on the required temperature of the drying chamber. The control system based on Arduino Uno board is built within the solar dryer, after which tests are carried out. The test results are displayed on a display. Themanagement system was set up to maintain an ambient temperature between 40 and 60 °C andrelative humidity between 10 and 20 %. The system is a flexible solution for different climatic zones and dried products, according to experimental findings demonstratingits efficiency in managing the drying environment. Finally, this paper can conserve energy because it only works when the temperature around the food is below 60 oC.

Use of Solar Energy for Disinfesting Stored Dates

A solar heat exposure or solarization trial was carried outduring November 2007 at Shambat Research Station, Sudan. TheObjective of the study was to control the date moth Ephestia calidella(Guen.) and the saw-toothed grain beetle Oryzaephilus surinamensis (L.)in stored dates. Black iron and polyethylene solar heat collectors wereconstructed and exposed to the sun. The results showed considerablevariation in the mean temperature between the iron heat collector,polyethylene heat collector and control treatments; they were 41.5C,53.7C and 57.4C, respectively, while the ambient mean temperature andrelative humidity were 33C and 52.9%. Six and 12 hours were enoughto control E. calidella in the iron heat and polyethylene heat collectors,respectively, and 18 and 24 hours to control O. surinamensis. Exposingthe ripened dates to a mean temperature of 57.4C for 24 hours did notlead to high significant change in the chemical composition, except thatsome sucrose was inverted to reducing sugars.

Impact of environmental temperature and relative humidity on spread of COVID-19 infection in India: a cross-sectional time-series analysis

Purpose: Coronavirus disease 2019 (COVID-19) has become a serious public health problem worldwide. This study sought to examine the associations of daily average temperature (AT) and relative humidity (ARH) with the percent increase in COVID-19 cases. Methods: Daily confirmed cases and meteorological factors in 38 districts of India were collected between 1st April 2020 to 30th April 2020. Taking a 5-day time lag of average values of the variables and multiple days-samples, we ran multiple models and performed appropriate hypothesis tests to decide the single preferred model for each sample data. Suitable fixed effects (FE) and random effects (RE) models with cluster-robust standard errors were applied to quantify the district-specific associations of meteorological and other variables with COVID-19 cases. Results: All FE models revealed that every one-degree rise in AT led to a decrease in 3.909 points (on average) in percent increase in COVID-19 cases. All RE models showed that with one unit increase in the malaria annual parasite index, there was a significant increase in 10.835 points (on average) in percent increase in COVID-19 cases. In both FE and RE models, ARH was found to be negatively associated with a percent increase in COVID-19 cases, although in half of these models the association was statistically insignificant. Conclusion: Our results indicate that mean temperature, mean relative humidity, and malaria endemicity might have an essential role in the stability and transmissibility of the 2019 novel coronavirus.

Controlled Environment Neutron Radiography of Moisture Sorption/Desorption in Nanocellulose-Treated Cotton Painting Canvases.

Nanocellulose-based materials have recently been used to consolidate degraded cotton painting canvases. Canvas-supported paintings consist of materials that are sensitive to moisture and especially susceptible to environmental fluctuations in temperature and relative humidity (RH). These environmental fluctuations occur in uncontrolled environments found in historic houses and palaces and can lead to hydrolytic degradation and mechanical damage to canvases. To simulate this situation in an experimental setting, canvas samples were mounted in a custom-made closed-cell and subjected to programmed cycles of RH at a controlled temperature while exposed to the neutron beam. Results are presented for both untreated samples and those treated with a polar consolidant, cellulose nanofibrils (CNF(aq)) in water, and an apolar consolidant, a composite of persilylated methyl cellulose with surface silylated cellulose nanocrystals (MC+CNC(h)) in heptane. They were then compared with changes in ionic conductivities as measured by dielectric analysis (DEA) with the same cyclic RH program and temperature. Although the samples were exposed to the same experimental conditions, they presented treatment-specific responses. CNF-treated canvas showed higher hygroscopicity than the untreated sample and facilitated moisture diffusion across the sample to areas not exposed to the environment. A sample treated with MC+CNC(h) retarded moisture diffusion during the increase in RH and could, therefore, afford protection to moisture absorption in uncontrolled environments. Thus, the experimental setup and resulting data provide a pilot study demonstrating the potential of neutron radiography in following and comparing real-time moisture diffusion dynamics in untreated and nanocellulose-consolidated cotton canvases and assisting in validating the overall benefit of the treatment.

Contribution of nitrous acid to the atmospheric oxidation capacity in an industrial zone in the Yangtze River Delta region of China

Abstract. A suite of instruments was deployed to simultaneously measure nitrous acid (HONO), nitrogen oxides (NOx = NO + NO2), carbon monoxide (CO), ozone (O3), volatile organic compounds (VOCs – including formaldehyde, HCHO) and meteorological parameters near a typical industrial zone in Nanjing in the Yangtze River Delta (YRD) region of China from 1 to 31 December 2015. High levels of HONO were detected using a wet-chemistry-based method. HONO ranged from 0.03 to 7.04 ppbv with an average of 1.32±0.92 ppbv. Elevated daytime HONO was frequently observed with a minimum of several hundred parts per trillion by volume (pptv) on average, which cannot be explained by the homogeneous OH + NO reaction (POH+NO) and primary emissions (Pemission), especially during periods with high particulate matter (PM2.5) loadings. HONO chemistry and its impact on the atmospheric oxidation capacity in the study area were further investigated using a Master Chemical Mechanism (MCM) box model. The results show that the average hydroxyl radical (OH) production rate was dominated by the photolysis of HONO (7.13×106 molec. cm−3 s−1), followed by the ozonolysis of alkenes (3.94×106 molec. cm−3 s−1), the photolysis of O3 (2.46×106 molec. cm−3 s−1) and the photolysis of HCHO (1.60×106 molec. cm−3 s−1) during the campaign period, especially within plumes that originated from the industrial zone. Model simulations indicated that heterogeneous chemistry played an important role in HONO formation. The average nighttime NO2 to HONO conversion rate was determined to be ∼0.8 % h−1. A good correlation between nocturnal HONO∕NO2 and the product of particle surface area density (S∕V) and relative humidity (RH), S/V⋅RH, supports the heterogeneous NO2∕H2O reaction mechanism. The other HONO source, designated as Punknonwn, was about twice as high as POH+NO on average and displayed a diurnal profile with an evidently photo-enhanced feature, i.e., photosensitized reactions of NO2 may be an important daytime HONO source. Nevertheless, our results suggest that daytime HONO formation was mostly due to the light-induced conversion of NO2 on aerosol surfaces, whereas heterogeneous NO2 reactions on the ground surface dominated nocturnal HONO production. Our study indicated that an elevated PM2.5 level during haze events can promote the conversion of NO2 to HONO by providing more heterogeneous reaction sites, thereby increasing the atmospheric oxidation capacity, which may further promote the formation of secondary air pollutants. Highlights: High levels of HONO, with an average of 1.32±0.92 ppbv, were observed near one of the largest industrial zones in the YRD region of China. HONO photolysis and alkene ozonolyses contributed the most to OH production and, hence, the atmospheric oxidation capacity. High loading of PM2.5 provided additional reaction surfaces for HONO formation. Heterogeneous formation mechanisms were the most important daytime HONO sources and were further enhanced by sunlight.

COVID-19 transmission in Mainland China is associated with temperature and humidity: A time-series analysis

COVID-19 has become a pandemic. The influence of meteorological factors on the transmission and spread of COVID-19 is of interest. This study sought to examine the associations of daily average temperature (AT) and relative humidity (ARH) with the daily counts of COVID-19 cases in 30 Chinese provinces (in Hubei from December 1, 2019 to February 11, 2020 and in other provinces from January 20, 2020 to Februarys 11, 2020). A Generalized Additive Model (GAM) was fitted to quantify the province-specific associations between meteorological variables and the daily cases of COVID-19 during the study periods. In the model, the 14-day exponential moving averages (EMAs) of AT and ARH, and their interaction were included with time trend and health-seeking behavior adjusted. Their spatial distributions were visualized. AT and ARH showed significantly negative associations with COVID-19 with a significant interaction between them (0.04, 95% confidence interval: 0.004–0.07) in Hubei. Every 1 °C increase in the AT led to a decrease in the daily confirmed cases by 36% to 57% when ARH was in the range from 67% to 85.5%. Every 1% increase in ARH led to a decrease in the daily confirmed cases by 11% to 22% when AT was in the range from 5.04 °C to 8.2 °C. However, these associations were not consistent throughout Mainland China.

Seasonal Variability of the Ion Composition, Phase State, and Mass Concentration of Aerosol in the Rural and Urban Atmosphere over Belgium (2001–2003)

Field data on the ion composition and mass concentration of aerosol in the rural (Wingene) and urban (Antwerp) regions of Belgium and the results of their thermodynamic analysis are presented. Ammonium nitrate and ammonium sulfate are found to be the major water-soluble components of aerosol particles. The seasonal variability of mass concentration, phase state, and ion composition of aerosol particles is largely determined by variations in temperature and relative humidity. It is shown that the content of ammonium nitrate and ammonium sulfate in PM2.5 is close to their thermodynamic equilibrium concentrations.

Impact of Variegated Temperature, CO<SUB>2</SUB> and Relative Humidity on Survival and Development of Beet Armyworm <i>Spodoptera exigua</i> (Hubner) under Controlled Growth Chamber

Climate change will have a noteworthy bearing on survival, development, and population dynamics of insect pests. Therefore, we contemplated the survival and development of beet army worm, Spodoptera exigua under different temperatures, (15˚C, 25˚C, 35˚C, and 45˚C), CO2 (350, 550, 750 ppm) and relative humidity (55%, 65%, 75% and 85%) regimes. Maximum larval and pupal weights were recorded in insects reared at 25˚C. The growth of S. exigua was faster at 35˚C (larval period 7.4 days and pupal period 4.5 days) than at lower temperatures. At 15˚C, the larval period was extended for 61.4 days and there was no adult emergence from the pupae till 90 days. The S. exigua hatchling was absent at 45˚C. The larval survival ranged from 31.6% - 57.2%, maximum survival was recorded at 25˚C, and minimum at 45˚C. The maximum (84.27%) and minimum adult emergence were recorded in insects reared at 25˚C and 35˚C respectively. Maximum fecundity (384.3 eggs/female) and egg viability (51.97%) were recorded in insects reared at 25˚C. Larval and pupal periods increased with an increase in CO2 concentration. The highest pupal weights (128.6 mg/larva) were recorded at 550 ppm. The highest larval survival (73.50%) was recorded at 550 ppm and minimum (37.00%) at 750 ppm CO2. Fecundity was the highest in insects reared at 550 ppm CO2 (657.4 eggs/female), and the lowest at 750 ppm. Maximum larval and pupal weights were recorded in insects reared at 75% relative humidity (RH). The growth rate of S. exigua was faster at 85% RH than at lower RH. The larval survival ranged between 40.0% - 58.5%. Maximum adult emergence (88.91%) was recorded in insects reared at 75% RH and minimum at 85% RH. Maximum fecundity (447.6 eggs/female) and the highest egg viability (72.95%) were recorded in insects reared at 75% and 65% RH respectively. Elevated temperatures and relative moistness will diminish the life cycle, while hoisted CO2 will drag the life expectancy. Therefore, there is a need for thorough assessment of the impact of climatic factors on the population dynamics of insect pests, crop losses, and sustainability of crop production.

Impact of Biotic and Abiotic Factors on the Population Dynamics of Bemisia tabaci (Genn.) and Tetranychus urticae (Koch) Infested Tomato Plant Lycopersicon esculentum L. at kafr El sheikh Governorate

Impact of abiotic (minimum–maximum temperatures andrelative humidity) and biotic factors ( Coccinella undecimpunctata, Syrphus corollae , Amblyseius swirskii, Nesidiocoristenuis and Chrysoperla carnea) on the population dynamicsof Bemisiatabaci (Genn.) and Tetranchys urticae (Koch) infesting tomato plant Lycopersiconesculentum L. at kafr El sheikhgovernorate, Egypt were studied on spring plantation of 2016 &2017 seasons. The analysis ofvariance revealed significant variation among dates of observations, lines andin their interaction for B. tabaci(Genn.), T. urticae (Koch) and their natural enemies. The mean number ofB. tabaci and T. urticaeduring the first season was higher than that was recorded during the secondseason. The percentage of explained variance (E.V.) of abiotic andbiotic altogether in the population densities of B.tabaci and T. urticae in the first season was stronger percentagevalues than second as (62% - 86%) and (94% - 77%) for eggs and nymphsof B.tabaci while (84% _ 77%) and (84% -98%) and for eggs and movable stages of T.urticae during spring of plantation 2016 &2017 seasons, respectively.

Hygroscopic growth study in the framework of EARLINET during the SLOPE I campaign: synergy of remote sensing and in situ instrumentation

Abstract. This study focuses on the analysis of aerosol hygroscopic growth during the Sierra Nevada Lidar AerOsol Profiling Experiment (SLOPE I) campaign by using the synergy of active and passive remote sensors at the ACTRIS Granada station and in situ instrumentation at a mountain station (Sierra Nevada, SNS). To this end, a methodology based on simultaneous measurements of aerosol profiles from an EARLINET multi-wavelength Raman lidar (RL) and relative humidity (RH) profiles obtained from a multi-instrumental approach is used. This approach is based on the combination of calibrated water vapor mixing ratio (r) profiles from RL and continuous temperature profiles from a microwave radiometer (MWR) for obtaining RH profiles with a reasonable vertical and temporal resolution. This methodology is validated against the traditional one that uses RH from co-located radiosounding (RS) measurements, obtaining differences in the hygroscopic growth parameter (γ) lower than 5 % between the methodology based on RS and the one presented here. Additionally, during the SLOPE I campaign the remote sensing methodology used for aerosol hygroscopic growth studies has been checked against Mie calculations of aerosol hygroscopic growth using in situ measurements of particle number size distribution and submicron chemical composition measured at SNS. The hygroscopic case observed during SLOPE I showed an increase in the particle backscatter coefficient at 355 and 532 nm with relative humidity (RH ranged between 78 and 98 %), but also a decrease in the backscatter-related Ångström exponent (AE) and particle linear depolarization ratio (PLDR), indicating that the particles became larger and more spherical due to hygroscopic processes. Vertical and horizontal wind analysis is performed by means of a co-located Doppler lidar system, in order to evaluate the horizontal and vertical dynamics of the air masses. Finally, the Hänel parameterization is applied to experimental data for both stations, and we found good agreement on γ measured with remote sensing (γ532=0.48±0.01 and γ355=0.40±0.01) with respect to the values calculated using Mie theory (γ532=0.53±0.02 and γ355=0.45±0.02), with relative differences between measurements and simulations lower than 9 % at 532 nm and 11 % at 355 nm.

Intercalibration between HIRS/2 and HIRS/3 channel 12 based on physical considerations

Abstract. High-resolution Infrared Radiation Sounder (HIRS) brightness temperatures at channel 12 (T12) can be used to assess the water vapour content of the upper troposphere. The transition from HIRS/2 to HIRS/3 in 1999 involved a shift in the central wavelength of channel 12 from 6.7 to 6.5 µm, causing a discontinuity in the time series of T12. To understand the impact of this change in the measured brightness temperatures, we have performed radiative transfer calculations for channel 12 of HIRS/2 and HIRS/3 instruments, using a large set of radiosonde profiles of temperature and relative humidity from three different sites. Other possible changes within the instrument, apart from the changed spectral response function, have been assumed to be of minor importance, and in fact, it was necessary to assume as a working hypothesis that the spectral and radiometric calibration of the two instruments did not change during the relatively short period of their common operation. For each radiosonde profile we performed two radiative transfer calculations, one using the HIRS/2 channel response function of NOAA 14 and one using the HIRS/3 channel response function of NOAA 15, resulting in negative differences of T12 (denoted as ΔT12:=T12/15-T12/14) ranging between −12 and −2 K. Inspection of individual profiles for large, medium and small values of ΔT12 pointed to the role of the mid-tropospheric humidity. This guided us to investigate the relation between ΔT12 and the channel 11 brightness temperatures which are typically used to detect signals from the mid-troposphere. This allowed us to construct a correction for the HIRS/3 T12, which leads to a pseudo-channel 12 brightness temperature as if a HIRS/2 instrument had measured it. By applying this correction we find an excellent agreement between the original HIRS/2 T12 and the HIRS/3 data inferred from the correction method with R=0.986. Upper-tropospheric humidity (UTH) derived from the pseudo HIRS/2 T12 data compared well with that calculated from intersatellite-calibrated data, providing independent justification for using the two intercalibrated time series (HIRS/2 and HIRS/3) as a continuous HIRS time series for long-term UTH analyses.

Predicting Field Generations of The Green Peach Aphid, Myzus persicae (Sulzer) and Its Predator, Green Lace-Wing, Chrysoperla carnea (Stephens) by Using Heat Units Accumulation and Evaluation of Some Insecticides against Their Populations

Applying a precise forecasting method is necessary to achieve acceptable results in integrated pest management programs.The objectives of this work were to predict the occurrence of population of Myzus persicae (Hemiptera: Aphididae) andChrysoperla carnea (Neuroptera: Chrysopidae), determine the influence of temperature and relative humidity on their populationdensities and also to study the effect of five insecticides on the population of these insect species in potato plants under fieldconditions at Nobaria district, El-Beheira Governorate, Egypt. The populations of M. persicae and C. carnea were monitored onpotato plants from February to May of 2015 and 2016 seasons. The population peaks of these insects were predicted using adegree-day model (accumulated thermal units). The obtained results revealed that the green peach aphid has nine fieldgenerations while the green lace-wing has two field generations. The general average of deviations between the expected peakscompared to the observed peaks were -1.333 and -1 days in case of M. persicae, while these averages were +3 and -1 days in caseof green lace-wing in 2015 and 2016 seasons, respectively. The effect of the meteorological factors such as temperature andrelative humidity on population of these insect were studied. The correlation results revealed that the incidence of M. persicaeand C. carnea were significantly and positively correlated in descending order with minimum, mean, and maximum temperaturedegree, respectively. The efficiency of acetamiprid, thiamethoxam, pymetrozine, chlorantraniliprole and pirimicarb on M.persicae and C. carnea populations was determined. These insecticides could be arranged in ascending order as: acetamiprid >thiamethoxam > chlorantraniliprole > pymetrozine > pirimicarb for controlling the green peach aphid. While regarding theirharmful effect on the C. carnea population their order became chlorantraniliprole > pirimicarb > thiamethoxam > acetamiprid >pymetrozine. These results were repeated in both seasons of study, 2015 and 2016.

POPULATION DYNAMICS OF DAGGER NEMATODE ATTACKING ALEPPO PINE TREE IN JORDAN

The temporal distribution of an isolate of the dagger nematode attacking Aleppopine, Pinus halepensis grown in AL-Jubiha area in Jordan was investigated. A totalof eighteen samples were collected from rhizosphere about 30 cm deep in soil and50 cm away from the trunk of a Pine tree showing decline and brown needles asone sample per month starting in November 2014 until April 2016. Cobb sievingand gravity methods were used for the nematode isolation from rhizosoil. The soiltype is clay with 51 % porosity. The monthly air temperature, precipitation, andrelative humidity were monitored and tabulated. The results showed that thenumber of recovered nematodes ranged from 2 individuals /100 cm3 to 88individuals /100cm3 of rhizosoil. The lowest number was recovered on Octoberwhereas the highest numbers were recovered in December. The reason of declinein numbers may be due to a raise in temperature. The highest number may be dueto favorable temperature and soil moisture. The difference of nematode in samemonth in two different years may be due to the temperature and precipitations.

Investigation of Ambient Factors Spatial Variability in Cold Stores by Using Management Zone Analysis

The main objective of this research was to determineand manage spatial variability of ambient temperature, relative humidity andair velocity in a cold storage using management zone analysis methods. Ambient temperature, relative humidity and airvelocity of an experimental cold storage were measured using 36 temperature andrelative humidity sensors. Sensor installation was performed on gridscale at three levels (base, middle and top) such as to monitor the coldstorage conditions of the total volume. Surfermapping system (Golden software Inc.) was utilized to create the maps of themeasured parameters and the collected data were analyzed by MZA software whichperformed fuzzy clustering to delineate the full cold storage, half full coldstorage and empty cold storage. Theresults indicated that there is significant spatial variation of the basic storageparameters such as temperature, relative humidity and air velocity in the coldstorage, which denotes the significance of management zones delineation inthese facilities so as to maximize the storage

A relative humidity calibration from 5°C to 45°C in a mixed-flow humidity generator

The paper presents a method used in the Vinca Institute of Nuclear Sciences for a reliable and traceable relative humidity calibration in the temperature range from 5?C to 45?C. Inside a controllable temperature and humidity environment, supplied by a mixed-flow humidity generator, measurements of hygrometers under calibration are compared with those of calibrated reference instruments. A traceability chain from temperature to reference relative humidity and next to the hygrometers under calibrations is provided by using a chilled-mirror dew-point temperature system and precise relative humidity probes. Corresponding calibration uncertainties are analyzed, particularly those associated to the temperature uniformity of controlled calibration environment. Two examples of relative humidity calibration with dew-point and relative humidity reference measurements in the range from 15 to 75% of RH and 5?C to 45?C are presented and discussed.

Monitoring of 7Be atmospheric activity concentration using short term measurements

The activity concentration of 7Be in atmospheric aerosol can exhibit seasonal variations due to various physical processes taking place in the troposphere and stratosphere, as well as due to solar activity. An investigation of these variations has been carried out at the Nuclear Engineering Department of the National Technical University of Athens over a two year period (3/2008-4/2010). In the framework of this study, sampling and analysis methods were appropriately selected to allow for the observation of short-term 7Be air activity concentration variations, using a 4-hour sampling interval, while taking in consideration type A and type B uncertainties introduced in the measurements. In order to study the role of precipitation in surface air 7Be activity concentration variations, a procedure for collecting and analyzing rainwater was developed. The techniques used in the present study allowed for the observation of seasonal and diurnal 7Be concentration variations, as well as correlations between 7Be activity concentration and the meteorological parameters of air temperature and relative humidity.

EFFECTS OF BIMONTHLY RAINFALL ON COCONUT YIELD IN THE LOW COUNTRY INTERMEDIATE ZONE (IL,) OF SRI LANKA

Coconut yields in Sri Lanka show considerable fluctuation between years mainly due tovariation in the distributions of major climatic parameters such as rainfall, solar radiation andrelative humidity. The effect of current weather is usually reflected on the yields of the followingyear. However, the degree of. influence of these variables on coconut yield is yet unknown. Anattempt was made to study the influence of intensity and distribution of rainfall in two-monthlysub-periods of the previous year on nut yield at Ratmalagara Estate in the Low Country DryIntermediate Zone (75% annual rainfall probability > 1500) of Sri Lanka. Rainfall during January/February was found to be the most influential factor on the subsequent years total yield and theyield increased with increasing rainfall. The rainfall during March/April had a similar effect wherearound 400 mm was found to be sufficient. The high intensity of rainfall during May/Augustadversely affected the crop, where amount in excess of 450 mm was not utilized to increase theyield. The impact of rain during July/August was minimal. High rainfall during September/October and November/December had a depressing effect on yield, and this was very significantwith respect to the November/December rainfall. A multiple regression model with R = 89% wasdeveloped using a combination of some parameters of bimonthly rainfall which would be usefulin determining the potential yield and to explain yield fluctuation between years to a certaindegree.

An analysis of drought events for central plains of Iran through an employment of NOAA-AVHRR data

Drought is a major problematic phenomenon for the mostly semi-arid country of Iran. The north centralregions of Iran (north of Esfahan and Ghom province) have suffered from severe droughts several times duringthe last three decades. The frequent occurrence of drought in these regions is due to low and inconsistentprecipitation, abnormally high temperatures, increases in surface albedo and evapotranspiration; especiallyduring spring. The surface characteristics of Kashan and Ghom regions consist of salty flats and sandy hillscovered by sparse vegetation. The average elevation of the area is 1987 mASL. In the present work, NOAAAVHRRdata have been employed to assess vegetation indices and environmental conditions in the study regionfor the years 1998 – 2004; which are then compared to actual ground data such as rainfall, temperature andrelative humidity for a detailed drought analysis. Spatial and temporal variations of meteorological droughts inKashan have been analyzed using Standardized Precipitation Index (SPI) at annual and seasonal scales, and havebeen generated through GIS based interpolation. Vegetative and thermal drought indices have been calculatedusing NDVI, VCI, and TCI values derived from NOAA-AVHRR data. Results from applying remotely senseddata show that this area is generally of low vegetation index values. The artificial forests and farmlands at thefoothills of the mountains northwest of Kashan region showed relatively high vegetation index values. TCI andVCI generally show a good relationship with meteorological observations. According to the output of utilizationNDVI and VCI, 2000 and 2001 years were characteristic of drought conditions, while 2002 and 2004 did nonrepresent drought years. Since TCI index is completely dependent on surface temperature, the combined analysisof the May and April results were influenced by the low land surface temperatures experienced in April, andtherefore it was very different from the other indices i.e. NDVI and VCI. Therefore thermal IR channels can beemployed used to monitor drought conditions in the semi-arid and arid regions of Iran to assess these regions,environmental conditions.

CONTROLLED ENVIRONMENT SYSTEM FOR STUDYING ROOT ZONE TEMPERATURE EFFECTS ON CUTTING PROPAGATION

An experimental controlled environment system for plant propagation was developed to provide three replications of a gradient in root zone temperature treatments to poinsettia cuttings. The system consisted of three propagation chambers and a transpiration chamber for water status tests. Control of VPDair and PAR was also possible. A unique component of the propagation chambers was the system of thermogradient tables that provided controlled bottom heating of the cutting medium in the root zone. Two different constant temperature water baths provided water that flowed through aluminum channels welded to opposite sides of an aluminum plate. The temperature of the two water sources could be set to provide a temperature gradient along the width of the plate. Cuttings were propagated in covered aluminum trays oriented along the length of the thermogradient table to provide multiple cuttings at different media temperatures. The thermogradient table maintained root zone temperatures within 0.5.C of all five treatment setpoints. The same source of plant material may be used for the replications, thus reducing the variability caused by differences in stock plant health and maintenance. Performance of the propagation chambers, some demonstrative results of use, and some limitations in ability to maintain air temperature and relative humidity in high radiation situations are presented.