scholarly journals Optical and Geometrical Properties of Cirrus Clouds in Amazonia Derived From 1-year of Ground-based Lidar Measurements

2016 ◽  
Author(s):  
Diego A. Gouveia ◽  
Boris Barja ◽  
Henrique M. J. Barbosa ◽  
Theotônio Pauliquevis ◽  
Paulo Artaxo
Keyword(s):  
Optical Depth ◽  
Diurnal Cycle ◽  
High Frequency ◽  
Dry Season ◽  
Cirrus Clouds ◽  
Cloud Base ◽  
Wet Season ◽  
Geometrical Properties ◽  
Lidar Ratio ◽  
The Mean

Abstract. For one year, from July 2011 to June 2012, a ground-based raman lidar provided atmospheric observations north of Manaus, Brazil, at an experimental site (2.89° S and 59.97° W) for long-term aerosol and cloud measurements. Upper tropospheric cirrus clouds were observed more frequently than previous reports in tropical regions. The frequency of occurrence was found to be as high as 82 % during the wet season and not lower than 55 % during the dry season. The diurnal cycle shows a minimum around local noon and maximum during late afternoon, associated with the diurnal cycle precipitation. Optical and geometrical characteristics of these cirrus clouds were derived. The mean values were 14.4 ± 2.0 km (top), 12.7 ± 2.3 km (base), 1.7 ± 1.5 km (thickness), and 0.36 ± 1.20 (cloud optical depth). Cirrus clouds were found at temperatures down to –90 °C and 7 % were above the tropopause base. The vertical distribution was not uniform and two cloud types were identified: (1) cloud base > 14 km and optical depth ~0.02, and (2) cloud base < 14 km and optical depth ~0.2. A third type, not previously reported, was identified during the wet season, between 16 and 18 km with optical depth ~0.005. The mean lidar ratio was 20.2 ± 7.0 sr, indicating a mixture of thick plates and long columns. However, the clouds above 14 km have a bimodal distribution during the dry season with a secondary peak at about 40 sr suggesting that thin plates are a major habit. A dependence of the lidar ratio with cloud temperature (altitude) was not found, thus indicating they are well mixed in the vertical. Cirrus clouds classified as subvisible (τ < 0.03) were 40 %, whilst 37.7 % were thin cirrus (0.03 < τ < 0.3) and 22.3 % opaque cirrus (τ > 0.3). Hence, not only does the central Amazon have a high frequency of cirrus clouds, but a large fraction of subvisible cirrus clouds as well. This high frequency of subvisible cirrus clouds may contaminate aerosol optical depth measured by sun-photometers and satellite sensors to an unknown extent.

scholarly journals Optical and geometrical properties of cirrus clouds in Amazonia derived from 1 year of ground-based lidar measurements

2017 ◽  
Vol 17 (5) ◽  
pp. 3619-3636 ◽  
Author(s):  
Diego A. Gouveia ◽  
Boris Barja ◽  
Henrique M. J. Barbosa ◽  
Patric Seifert ◽  
Holger Baars ◽  
...  
Keyword(s):  
Optical Properties ◽  
Diurnal Cycle ◽  
High Frequency ◽  
Large Fraction ◽  
Cirrus Clouds ◽  
Frequency Of Occurrence ◽  
Geometrical Properties ◽  
Lidar Ratio ◽  
The Mean ◽  
Ground Based Lidar

Abstract. Cirrus clouds cover a large fraction of tropical latitudes and play an important role in Earth's radiation budget. Their optical properties, altitude, vertical and horizontal coverage control their radiative forcing, and hence detailed cirrus measurements at different geographical locations are of utmost importance. Studies reporting cirrus properties over tropical rain forests like the Amazon, however, are scarce. Studies with satellite profilers do not give information on the diurnal cycle, and the satellite imagers do not report on the cloud vertical structure. At the same time, ground-based lidar studies are restricted to a few case studies. In this paper, we derive the first comprehensive statistics of optical and geometrical properties of upper-tropospheric cirrus clouds in Amazonia. We used 1 year (July 2011 to June 2012) of ground-based lidar atmospheric observations north of Manaus, Brazil. This dataset was processed by an automatic cloud detection and optical properties retrieval algorithm. Upper-tropospheric cirrus clouds were observed more frequently than reported previously for tropical regions. The frequency of occurrence was found to be as high as 88 % during the wet season and not lower than 50 % during the dry season. The diurnal cycle shows a minimum around local noon and maximum during late afternoon, associated with the diurnal cycle of precipitation. The mean values of cirrus cloud top and base heights, cloud thickness, and cloud optical depth were 14.3 ± 1.9 (SD) km, 12.9 ± 2.2 km, 1.4 ± 1.1 km, and 0.25 ± 0.46, respectively. Cirrus clouds were found at temperatures down to −90 °C. Frequently cirrus were observed within the tropical tropopause layer (TTL), which are likely associated to slow mesoscale uplifting or to the remnants of overshooting convection. The vertical distribution was not uniform, and thin and subvisible cirrus occurred more frequently closer to the tropopause. The mean lidar ratio was 23.3 ± 8.0 sr. However, for subvisible cirrus clouds a bimodal distribution with a secondary peak at about 44 sr was found suggesting a mixed composition. A dependence of the lidar ratio with cloud temperature (altitude) was not found, indicating that the clouds are vertically well mixed. The frequency of occurrence of cirrus clouds classified as subvisible (τ < 0. 03) were 41.6 %, whilst 37.8 % were thin cirrus (0. 03 < τ < 0. 3) and 20.5 % opaque cirrus (τ > 0. 3). Hence, in central Amazonia not only a high frequency of cirrus clouds occurs, but also a large fraction of subvisible cirrus clouds. This high frequency of subvisible cirrus clouds may contaminate aerosol optical depth measured by sun photometers and satellite sensors to an unknown extent.

scholarly journals Statistics of vertical backscatter profiles of cirrus clouds

2011 ◽  
Vol 11 (24) ◽  
pp. 12925-12943 ◽  
Author(s):  
P. Veglio ◽  
T. Maestri
Keyword(s):  
Optical Depth ◽  
Satellite Observation ◽  
Cirrus Clouds ◽  
Cloud Base ◽  
Physical Parameters ◽  
Cloud Optical Depth ◽  
Cloud Temperature ◽  
The Mean ◽  
Depth Increase ◽  
The Impact

Abstract. A nearly global statistical analysis of vertical backscatter and extinction profiles of cirrus clouds collected by the CALIOP lidar, on-board of the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation, is presented. Statistics on frequency of occurrence and distribution of bulk properties of cirrus clouds in general and, for the first time, of horizontally homogeneous (on a 5-km field of view) cirrus clouds only are provided. Annual and seasonal backscatter profiles (BSP) are computed for the horizontally homogeneous cirri. Differences found in the day/night cases and for midlatitudes and tropics are studied in terms of the mean physical parameters of the clouds from which they are derived. The relationship between cloud physical parameters (optical depth, geometrical thickness and temperature) and the shape of the BSP is investigated. It is found that cloud geometrical thickness is the main parameter affecting the shape of the mean CALIOP BSP. Specifically, cirrus clouds with small geometrical thicknesses show a maximum in mean BSP curve located near cloud top. As the cloud geometrical thickness increases the BSP maximum shifts towards cloud base. Cloud optical depth and temperature have smaller effects on the shape of the CALIOP BSPs. In general a slight increase in the BSP maximum is observed as cloud temperature and optical depth increase. In order to fit mean BSPs, as functions of geometrical thickness and position within the cloud layer, polynomial functions are provided. The impact on satellite radiative transfer simulations in the infrared spectrum when using either a constant ice-content (IWC) along the cloud vertical dimension or an IWC profile derived from the BSP fitting functions is evaluated. It is, in fact, demonstrated that, under realistic hypotheses, the mean BSP is linearly proportional to the IWC profile.

scholarly journals Optical and Geometrical Properties of Cirrus Clouds over the Tibetan Plateau Measured by LiDAR and Radiosonde Sounding during the Summertime in 2014

2019 ◽  
Vol 11 (3) ◽  
pp. 302 ◽  
Author(s):  
Guangyao Dai ◽  
Songhua Wu ◽  
Xiaoquan Song ◽  
Liping Liu
Keyword(s):  
Tibetan Plateau ◽  
Optical Depth ◽  
Extinction Coefficient ◽  
Mean Value ◽  
Cirrus Clouds ◽  
The Tibetan Plateau ◽  
Convective Activity ◽  
Depolarization Ratio ◽  
Geometrical Properties ◽  
The Mean

Optical and geometrical characteristics of the cirrus clouds over Naqu (4508 m a.s.l., 31.48° N, 92.06° E), in the Tibetan Plateau were determined from LiDAR and radiosonde measurements performed during the third TIbetan Plateau EXperiment of atmospheric sciences (TIPEX III) campaign from July to August 2014. For the analysis of the temperature dependence, the simultaneous observations with LiDAR and radiosonde were conducted. Cirrus clouds were generally observed ranging from 5.2 km to 12 km above ground level (AGL) (i.e., 9.7 km to 16.5 km a.s.l.), with the midcloud temperatures ranging from −79.7 to −26.0 °C. The cloud thickness generally differed from 0.12 to 2.55 km with a mean thickness of 1.22 ± 0.70 km, and 85.7% of the measurement cases had thickness smaller than 1.5 km. The retrievals of linear particle depolarization ratio, extinction coefficient, and optical depth of cirrus clouds were provided. Moreover, the multiple scattering effect inside of cirrus clouds was corrected. The linear particle depolarization ratio of the cirrus clouds varied from 0.36 to 0.52, with a mean value of 0.44 ± 0.04. The optical depth of the cirrus clouds was between 0.01 and 3 following the scheme of Fernald-Klett method. Sub-visual, thin, and opaque cirrus clouds were observed at 4.76%, 61.90% and 33.34% of the measured cases, respectively. The temperature and thickness dependencies of the optical properties were studied in detail. A maximum cirrus thickness of around 2 km was found at temperatures between −60 and −50 °C. This study shows that the mean extinction coefficient of the cirrus clouds increases with the increase of temperature. Conversely, the measurements indicate that the linear particle depolarization ratio decreases with the increasing temperature. The relationships between the existence of cirrus clouds and the temperature anomaly (temperature difference from the mean value of the temperature during July and August 2014 over Naqu) and deep convective activity are also discussed. The formation of cirrus clouds is investigated and also its apparent relationship with the South Asia High Pressure, the dynamic processes of Rossby wave, and deep convective activity over the Tibetan Plateau. The outgoing longwave radiation of cirrus clouds is calculated with the Fu-Liou model and is shown to increases monotonously with the increase of optical depth.

scholarly journals Statistics of vertical backscatter profile of cirrus clouds

2011 ◽  
Vol 11 (9) ◽  
pp. 25813-25870
Author(s):  
P. Veglio ◽  
T. Maestri
Keyword(s):  
Optical Depth ◽  
Satellite Observation ◽  
Cirrus Clouds ◽  
Cloud Base ◽  
Physical Parameters ◽  
Cloud Optical Depth ◽  
Cloud Temperature ◽  
The Mean ◽  
Depth Increase ◽  
The Impact

Abstract. A nearly global statistical analysis of vertical backscatter and extinction profiles of cirrus clouds collected by the CALIOP lidar, on-board of the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation, is presented. Statistics on frequency of occurrence and distributions of bulk properties of cirrus clouds in general and, for the first time, of horizontally homogeneous (on a 5-km field of view) cirrus clouds only are provided. Annual and seasonal backscatter profiles (BSP) are computed for the horizontally homogeneous cirri. Differences found in the day/night cases and for midlatitudes and tropics are studied in terms of the mean physical parameters of the clouds from which they are derived. The relation between cloud physical parameters (optical depth, geometrical thickness and temperature) and the shape of the BSP is investigated. It is found that cloud geometrical thickness is the main parameter affecting the shape of the mean CALIOP BSP. Specifically, cirrus clouds with small geometrical thicknesses show a maximum in mean BSP curve placed near cloud top. As the cloud geometrical thickness increases the BSP maximum shifts towards cloud base. Cloud optical depth and temperature have smaller effect on the shape of the CALIOP BSPs. In general a slight increase in the BSP maximum is observed as cloud temperature and optical depth increase. In order to fit mean BSPs, as functions of geometrical thickness and position within the cloud layer, polynomial functions are provided. The impact on satellite radiative transfer simulations in the infrared spectrum when using either a constant ice-content (IWC) along the cloud vertical dimension or an IWC profile derived from the BSP fitting functions is evaluated. It is, in fact, demonstrated that, under realistic hypotheses, the mean BSP is linearly proportional to the IWC profile.

scholarly journals Investigation of Heavy Metals Level in selected Boreholes around the Vicinity of some Cemeteries in Benin City, Nigeria

2021 ◽  
Vol 25 (5) ◽  
pp. 841-845
Author(s):  
C.A.E. Ibhadode ◽  
I.R. Ilaboya
Keyword(s):  
Heavy Metals ◽  
Pollution Index ◽  
Mean Value ◽  
Dry Season ◽  
Wet Season ◽  
Monthly Basis ◽  
Benin City ◽  
Standard Procedures ◽  
The Mean ◽  
Mean Concentration

Groundwater pollution by heavy metals such as lead, copper, nickel and iron is one of the major environmental issues of concern which has developed into a widely studied area. In this study, attempt was made to investigate the level of heavy metals in selected boreholes around the vicinity of cemeteries in Benin City. Seventy-two (72) samples of groundwater were taken from boreholes in 9 stations around the three cemeteries in Benin City on monthly basis. The samples were analysed for 7 heavy metals, in accordance with standard procedures. The heavy metals include; Zinc, Lead Iron, Copper, Cadmium, Nickel and Mercury. From the results of the study, a variation in the mean concentration of zinc was observed. The mean concentration of zinc in site 1 was 0.450mg/l, for site 2, it was 0.140mg/l and for site 3, it was 1.0533mg/l. For iron, mean concentration was 0.072mg/l in site 1. For site 2, mean concentration of iron was 2.140mg/l and for site 3, mean concentration of iron was 0.560mg/l. It was further revealed based on the results that mean value of heavy metals in groundwater around cemeteries in Benin City were generally lower during dry season compared to wet season. In addition, result of computed pollution index (Pi) revealed that the heavy metal with the highest potential to pollute groundwater is Cadmium, with Pi of 0.5333 and 0.400 representing dry season and wet season respectively.

scholarly journals Aircraft observations of the chemical composition and aging of aerosol in the Manaus urban plume during GoAmazon 2014/5

2018 ◽  
Vol 18 (14) ◽  
pp. 10773-10797 ◽  
Author(s):  
John E. Shilling ◽  
Mikhail S. Pekour ◽  
Edward C. Fortner ◽  
Paulo Artaxo ◽  
Suzane de Sá ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Oxidation State ◽  
Biomass Burning ◽  
Urban Pollution ◽  
Organic Aerosol ◽  
Dry Season ◽  
Carbon Oxidation ◽  
Wet Season ◽  
The Mean ◽  
American Cities

Abstract. The Green Ocean Amazon (GoAmazon 2014/5) campaign, conducted from January 2014 to December 2015 in the vicinity of Manaus, Brazil, was designed to study the aerosol life cycle and aerosol–cloud interactions in both pristine and anthropogenically influenced conditions. As part of this campaign, the U.S. Department of Energy (DOE) Gulfstream 1 (G-1) research aircraft was deployed from 17 February to 25 March 2014 (wet season) and 6 September to 5 October 2014 (dry season) to investigate aerosol and cloud properties aloft. Here, we present results from the G-1 deployments focusing on measurements of the aerosol chemical composition and secondary organic aerosol (SOA) formation and aging. In the first portion of the paper, we provide an overview of the data and compare and contrast the data from the wet and dry season. Organic aerosol (OA) dominates the deployment-averaged chemical composition, comprising 80 % of the non-refractory PM1 aerosol mass, with sulfate comprising 14 %, nitrate 2 %, and ammonium 4 %. This product distribution was unchanged between seasons, despite the fact that total aerosol loading was significantly higher in the dry season and that regional and local biomass burning was a significant source of OA mass in the dry, but not wet, season. However, the OA was more oxidized in the dry season, with the median of the mean carbon oxidation state increasing from −0.45 in the wet season to −0.02 in the dry season. In the second portion of the paper, we discuss the evolution of the Manaus plume, focusing on 13 March 2014, one of the exemplary days in the wet season. On this flight, we observe a clear increase in OA concentrations in the Manaus plume relative to the background. As the plume is transported downwind and ages, we observe dynamic changes in the OA. The mean carbon oxidation state of the OA increases from −0.6 to −0.45 during the 4–5 h of photochemical aging. Hydrocarbon-like organic aerosol (HOA) mass is lost, with ΔHOA∕ΔCO values decreasing from 17.6 µg m−3 ppmv−1 over Manaus to 10.6 µg m−3 ppmv−1 95 km downwind. Loss of HOA is balanced out by formation of oxygenated organic aerosol (OOA), with ΔOOA∕ΔCO increasing from 9.2 to 23.1 µg m−3 ppmv−1. Because hydrocarbon-like organic aerosol (HOA) loss is balanced by OOA formation, we observe little change in the net Δorg∕ΔCO values; Δorg∕ΔCO averages 31 µg m−3 ppmv−1 and does not increase with aging. Analysis of the Manaus plume evolution using data from two additional flights in the wet season showed similar trends in Δorg∕ΔCO to the 13 March flight; Δorg∕ΔCO values averaged 34 µg m−3 ppmv−1 and showed little change over 4–6.5 h of aging. Our observation of constant Δorg∕ΔCO are in contrast to literature studies of the outflow of several North American cities, which report significant increases in Δorg∕ΔCO for the first day of plume aging. These observations suggest that SOA formation in the Manaus plume occurs, at least in part, by a different mechanism than observed in urban outflow plumes in most other literature studies. Constant Δorg∕ΔCO with plume aging has been observed in many biomass burning plumes, but we are unaware of reports of fresh urban emissions aging in this manner. These observations show that urban pollution emitted from Manaus in the wet season forms less particulate downwind as it ages than urban pollution emitted from North American cities.

The water intake of milking cows grazing Pangola grass (Digitaria decumbens Stent.) under wet- and dry-season conditions in Trinidad

1962 ◽  
Vol 58 (2) ◽  
pp. 257-264 ◽  
Author(s):  
P. N. Wilson ◽  
M. A. Barratt ◽  
M. H. Butterworth
Keyword(s):  
Water Intake ◽  
Free Water ◽  
Dry Season ◽  
Feed Water ◽  
Zebu Cattle ◽  
Wet Season ◽  
Drinking Habits ◽  
Digitaria Decumbens ◽  
Coefficients Of Variation ◽  
The Mean

1. The water intakes of ten Holstein × Zebu milking cows, yielding between one and two gallons of milk a day, were analysed on the basis of (a) freewater drunk, and (b) feed-water consumed with the herbage. Trials took place during a 10-day period in both the wet season, 1959 and the dry season, 1960. During both seasons the cows were rotationally grazed on Pangola grass pastures.2. The results showed a difference of only 24% in total water intake between seasons. However, the mean intake of free water increased from 18·5 lb. per cow in the wet season to 81·5 lb. per cow per day in the dry season, and the intake of feed water decreased from 94·9 to 59·2 lb. per cow per day, respectively. The between cow coefficients of variation were 9·7 and 8·7%, respectively.3. Results are presented for the drinking habits of Holstein × Zebu cattle grazing Pangola grass pastures. For 567 observed cow-days in the wet season, the cattle were found to drink water on average 0·8 times per day from troughs present in the pastures. For 332 observed cow-days in the dry season, the cattle increased their drinking habits to a mean figure of 1·4 times each day.

Seasonal evapotranspiration of irrigated cotton in a low-latitude environment

1967 ◽  
Vol 18 (2) ◽  
pp. 259 ◽  
Author(s):  
WR Stern
Keyword(s):  
Meteorological Factors ◽  
Ground Cover ◽  
Dry Season ◽  
Potential Evaporation ◽  
Crop Water ◽  
Wet Season ◽  
Low Latitude ◽  
Area Index ◽  
The Mean ◽  
Dominant Influence

Evapotranspiration (Et) from irrigated cotton was determined on a sequence of plantings covering a whole year. Averaged over the year, evapotranspiration directly after irrigation (Et1) was greater than the Penman estimate of potential evaporation (E) but less than the evaporation from a standard Australian tank (Etank). The mean annual ratios were 1.2 for Et1/E and 0.9 for Et1/Etank. The rate of evapotranspiration was a function of soil moisture, declining rapidly as the available moisture fell below 60 %. Because of the high variability in the estimates of evapotranspiration it was not possible to evaluate precisely the influence of growth stage on evapotranspiration. Although there was evidence that evapotranspiration varied with the stage of growth, meteorological factors were a dominant influence because of the high watering regime. Overall, a crop planted in the wet season used little more water than a crop planted in the dry season. After the maximum leaf area index (LAI) had been reached, evapotranspiration in the wet season crop declined more rapidly and fell to a lower value than evapotranspiration during the corresponding period in the dry season crop. Water was used more efficiently by the wet season crop than by the dry season crop. The conclusion was reached that in this environment advection of energy persisted for most of the year, and that during periods of rapid height increases, particularly when ground cover was incomplete, crop surface roughness enhanced evapotranspiration. The possible interactions of some of the factors influencing evapotranspiration in a crop in the field are discussed.

A study of the growth rate of F2 and F3 Africander cross, Brahman cross and British cross cattle from birth to 18 months in a tropical environment

1971 ◽  
Vol 11 (53) ◽  
pp. 593 ◽  
Author(s):  
JF Kennedy ◽  
GIK Chirchir
Keyword(s):  
Growth Rate ◽  
Rank Order ◽  
Growth Period ◽  
Dry Season ◽  
Tropical Environment ◽  
Wet Season ◽  
Male And Female ◽  
The Mean

The mean birthweights and weaning weights of approximately 1200 male and female calves of the F2 and F3 generations of Africander cross (AX), Brahman cross (BX) and Shorthorn X Hereford cross (SH) cattle, together with the weights at four months, and nine months post weaning for approximately 500 of the females, for the years 1964-1968, are presented. BX calves (29.7 kg) were lighter at birth than AX (31.0 kg) or SH (31.8 kg), but at weaning (eight-nine months) they were 13.7 kg heavier than the AX, and 28.9 kg heavier than the SH. In the first four months postweaning, at the end of the dry-season, female AX gained 21.5 kg, BX gained 18.5 kg, and the SH 11.7 kg, and in the next five months, which included the wet-season, AX gained 78.6 kg, BX 83.1 kg, and SH 63.2 kg. At approximately eighteen months old the AX weighed 282.8 kg, BX 294.8 kg, and SH 244.2 kg. There were substantial differences between years but the rank order of the breeds at each growth period did not change.

Evaluation of management options for increasing the productivity of tropical savanna pastures. 3. Trees

1989 ◽  
Vol 29 (5) ◽  
pp. 631 ◽  
Author(s):  
WH Winter ◽  
JJ Mott ◽  
RW McLean
Keyword(s):  
Dry Season ◽  
Perennial Grasses ◽  
Fertility Level ◽  
Wet Season ◽  
Management Options ◽  
Themeda Triandra ◽  
Weight Losses ◽  
Nitrogen Concentrations ◽  
The Mean ◽  
Stocking Rates

The effect of killing trees upon the production and quality of native perennial grasses, Themeda triandra, Chrysopogon fallax, Sehima nervosum, and Sorghum plumosum, and oversown legumes from the genus Stylosanthes, was studied over 4 years at Katherine, in the semi-arid tropics of northwestern Australia. The pastures were either unfertilised or received low inputs of superphosphate, and for each fertility level were grazed at 3 stocking rates. At no time were legume yields affected by killing the trees but, in the first 3 years, the amount of grass was approximately twice as much when the trees were killed. During this period the mean grass yields declined 4-5 fold from about 2.2 t/ha. By the fourth year the advantage from tree killing upon grass yield was apparent only at the lowest stocking rates at each fertility level. Nitrogen concentrations of the grasses and legumes, with the exception of S. hamata, were increased 7 and 10% respectively above the mean annual values of 0.89 and 1.75% where the trees were killed, while the phosphorus and sulfur concentrations were not affected. Tree killing had no effect upon wet season liveweight gains during the last 2 years of the experiment. However, there were some benefits during the dry season when weight losses were lower for most treatments during the early dry season (June-September) and also lower for the lowest stocking rate treatment without fertiliser during the late dry season (October-November).

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