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1.
On February 8, 1993, the NASA DC-8 aircraft profiled from 10,000 to 37,000 feet (3.1–11.3 km) pressure altitude in a stratified section of tropical cyclone “Oliver” over the Coral Sea northeast of Australia. Size, shape and phase of cloud and precipitation particles were measured with a 2-D Greyscale probe. Cloud/ precipitation particles changed from liquid to ice as soon as the freezing level was reached near 17,000 feet (5.2 km) pressure altitude. The cloud was completely glaciated at −5°C. There was no correlation between ice particle habit and ambient temperature. In the liquid phase, the precipitation-cloud drop concentration was 4.0 × 103 m−3, the geometric mean diameter Dg=0.5−0.7 mm, and the liquid water content 0.7−1.9 g m−3. The largest particles anywhere in the cloud, dominated by fused dendrites at concentrations similar to that of raindrops (2.5 × 103 m−3) but a higher condensed water content (5.4 g m−3 estimated) were found in the mixed phase; condensed water is removed very effectively from the mixed layer due to high settling velocities of the large mixed particles. The highest number concentration (4.9 × 104 m−3), smallest size (Dg=0.3−0.4 mm), largest surface area (up to 2.6 × 102 cm2 m−3 at 0.4−1.0 g m−3 of condensate) existed in the ice phase at the coldest temperature (−40°C) at 35,000 feet (10.7 km). Each cloud contained aerosol (haze particles) in addition to cloud particles. The aerosol total surface area exceeded that of the cirrus particles at the coldest temperature. Thus, aerosols must play a significant role in the upscattering of solar radiation. Light extinction (6.2 km−1) and backscatter (0.8 sr−1 km−1) was highest in the coldest portion of the cirrus cloud at the highest altitude.  相似文献   

2.
By making use of TOVS Path-B satellite retrievals and ECMWF reanalyses, correlations between bulk microphysical properties of large-scale semi-transparent cirrus (visible optical thickness between 0.7 and 3.8) and thermodynamic and dynamic properties of the surrounding atmosphere have been studied on a global scale. These clouds constitute about half of all high clouds. The global averages (from 60°N to 60°S) of mean ice crystal diameter, De, and ice water path (IWP) of these clouds are 55 μm and 30 g m−2, respectively. IWP of these cirrus is slightly increasing with cloud-top temperature, whereas De of cold cirrus does not depend on this parameter. Correlations between De and IWp of large-scale cirrus seem to be different in the midlatitudes and in the tropics. However, we observe in general stronger correlations between De and IWP and atmospheric humidity and winds deduced from the ECMWF reanalyses: De and IWP increase both with increasing atmospheric water vapour. There is also a good distinction between different dynamical situations: In humid situations, IWP is on average about 10 gm−2 larger in regions with strong large-scale vertical updraft only that in regions with strong large-scale horizontal winds only, whereas the mean De of cold large-scale cirrus decreases by about 10 μm if both strong large-scale updraft and horizontal winds are present.  相似文献   

3.
Measurements of natural ice nuclei with a continuous flow diffusion chamber   总被引：1，自引：0，他引：1  
Measurements of natural ice nuclei were made in winter continental airmasses with a continuous flow thermal gradient diffusion chamber (described in a separate paper). Over the range of temperatures −7°C to −20°C, the concentration of ice nuclei was closely related to ice supersaturation (SSi) for humidities both below and above water saturation. Measurements below water saturation were interpreted as deposition nuclei with average concentrations (per liter) approximately 0.32 SSi(%)0.81. Measurements were made up to 5% above water saturation and activated both deposition and condensation-freezing nuclei. The average concentration of condensation-freezing nuclei was 0.25 e−0.15 T(°C). Sample residence time in the chamber was probably too small to detect contact nuclei, unless the nucleating aerosols are extremely small. There was large variability in nucleus concentrations, as much as two orders of magnitude at −15°C. Comparisons are made between these ice nuclei measurements and aircraft observations of ice crystal concentrations in winter orographic clouds.  相似文献   

4.
Cirrus clouds related to transported dust layers were identified on 22 occasions with ground-based polarization lidar from December 2012 to February 2018 over Wuhan (30.5°N, 114.4°E), China. All the events occurred in spring and winter. Cirrus clouds were mostly located above 7.6 km on top of the aloft dust layers. In-cloud relative humidity with respect to ice (RHi) derived from water vapor Raman lidar as well as from ERA5 reanalysis data were used as criteria to determine the possible ice nucleation regimes. Corresponding to the two typical cases shown, the observed events can be classified into two categories: (1) category A (3 cases), in-cloud peak RHi ≥ 150%, indicating competition between heterogeneous nucleation and homogeneous nucleation; and (2) category B (19 cases), in-cloud peak RHi < 150%, revealing that only heterogeneous nucleation was involved. Heterogeneous nucleation generally took place during instances of cirrus cloud formation in the upper troposphere when advected dust particles were present. Although accompanying cloud-top temperatures ranged from –51.9°C to –30.4°C, dust-related heterogeneous nucleation contributed to primary ice nucleation in cirrus clouds by providing ice nucleating particle concentrations on the order of 10?3 L?1 to 102 L?1. Heterogeneous nucleation and subsequent crystal growth reduced the ambient RHi to be less than 150% by consuming water vapor and thus completely inhibited homogeneous nucleation.  相似文献   

5.
Observations have been made of the ice-crystal morphology of snow which fell at two sampling sites during a warm front followed by a cold front in the Sierra Nevada of the western United States. The snow sampling and ice crystal observations were conducted at Kingvale (KV) and Hobart Mills (HM), California, which are located at almost identical elevations on the upwind and down wind sides of the Sierra Nevada crest, respectively.These observations and several mesoscale features of one of the storms, have been used to study the substantial changes which occurred in the stable oxygen isotopic composition (δ18O) of the precipitation at the two sites.At the beginning of the period of observation, a low level warm front lay across the region and its elevation lowered with time from 2.5 km to 1.7 km. This decrease of the frontal surface height was accompanied by a steady increase in the δ18O values.In the pre-cold frontal passage time periods, the δ18O values at the upwind site signified warmer origin ice crystal morphology than the downwind site. This is explained by orographic effects and the production of supercooled liquid water at low elevations on the upslope side of the Sierra Nevada.During the passage of the surface cold front, the differences in δ18O at the two sites were quite small probably because the orography plays a less significant role in the precipitation production process during such events.The δ18O peaked around −13% which translates to an “equivalent temperature” of −10.7°C for ice phase water capture at the upwind site KV. At site HM downwind of the Sierra crest, and 25 km east of KV, the weighted mean ice phase water capture occurred at elevations some 5 to 6°C colder than at KV, because of subsidence and loss of supercooled liquid water in the lower elevations on the lee side.  相似文献   

6.
Based on earlier experimental studies, the ice nucleating abilities of further pollen types were investigated in the immersion and contact freezing modes. The studies were carried out at the Mainz vertical wind tunnel with freely floating supercooled droplets down to − 28 °C. The pollen had diameters between 26 and 28 μm and correspondingly low sink velocities around 2.5 cm s− 1. The radii of the studied drops were calculated from the recorded wind velocity and for both freezing modes the radii of the observed droplets varied between 315 and 380 μm. Immersion freezing experiments were conducted with pollen particles added to the droplets while in contact freezing experiments supercooled droplets were subjected to a burst of pollen particles. The median freezing temperatures found in the immersion freezing mode were: − 13.5 °C (alder), − 21.5 °C (lombardy poplar), − 21.0 °C (redtop grass) and − 19.8 °C (kentucky blue). The median freezing temperatures in the contact freezing mode were found as: − 12.6 °C (alder), − 17.9 °C (lombardy poplar), − 18.7 °C (redtop grass) and − 16.1 °C (kentucky blue). The results show that the ice nucleating ability of pollen is not restricted to single pollen types but seems to be a general pollen property.  相似文献   

7.
Based on 1-year cloud measurements with radar and microwave radiometer broadband solar radiative transfer simulations were performed to quantify the impact of different ice crystal shapes of Arctic mixed-phase clouds on their radiative properties (reflectance, transmittance and absorptance). The ice crystal shape effects were investigated as a function of microphysical cloud properties (ice volume fraction fi, ice and liquid water content IWC and LWC, mean particle diameter DmI and DmW of ice/water particle number size distributions, NSDs).The required NSDs were statistically derived from radar data. The NSD was composed of a liquid and a solid mode defined by LWC, DmW (water mode) and IWC, DmI (ice mode). It was found that the ratio of DmI and DmW determines the magnitude of the shape effect. For mixed-phase clouds with DmI ≤ 27 μm a significant shape effect was obtained. The shape effect was almost insensitive with regard to the solar zenith angle, but highly sensitive to the ice volume fraction of the mixed-phase cloud. For mixed-phase clouds containing small ice crystals (DmI ≤ 27 μm) and high ice volume fractions (fi > 0.5) crystal shape is crucial. The largest shape effects were observed assuming aggregates and columns. If the IWC was conserved the shape effect reaches values up to 0.23 in cloud reflectance and transmittance. If the ice mode NSD was kept constant only a small shape effect was quantified (≤ 0.04).  相似文献   

8.
It is essential to quantify the background reactivity of smog-chambers, since this might be the major limitation of experiments carried out at low pollutant concentrations typical of the polluted atmosphere. Detailed investigation of three chamber experiments at zero-NO x in the European Photoreactor (EUPHORE) were carried out by means of rate-of-production analysis and two uncertainty analysis tools: local uncertainty analysis and Monte Carlo simulations with Latin hypercube sampling. The chemical mechanism employed was that for methane plus the inorganic subset of the Master Chemical Mechanism (MCMv3.1). Newly installed instruments in EUPHORE allowed the measurement of nitrous acid and formaldehyde at sub-ppb concentrations with high sensitivity. The presence of HONO and HCHO during the experiments could be explained only by processes taking place on the FEP Teflon walls. The HONO production rate can be described by the empirical equation W(HONO)EUPHORE dry = a × j NO 2× exp (− T 0/T) in the low relative humidity region (RH < 2%, a = 7.3×1021 cm−3, T 0 = 8945K), and by the equation W(HONO)EUPHORE humid = W(HONO)EUPHORE dry+ j NO 2× b × RH q in the higher relative humidity region (2% < RH < 15%, b = 5.8×108 cm−3 and q = 0.36, and RH is the relative humidity in percentages). For HCHO the expression W(HCHO)EUPHORE = c × j NO 2exp (− T′0/T) is applicable (c = 3.1×1017 cm−3 and T′0 = 5686 K). In the 0–15% relative humidity range OH production from HONO generated at the wall is about a factor of two higher than that from the photolysis of 100 ppb ozone. Effect of added NO2 was found to be consistent with the dark HONO formation rate coefficient of MCMv3.1.  相似文献   

9.
The remarkable wide range spatial scaling of TRMM precipitation   总被引：1，自引：0，他引：1  
The advent of space borne precipitation radar has opened up the possibility of studying the variability of global precipitation over huge ranges of scale while avoiding many of the calibration and sparse network problems which plague ground based rain gage and radar networks. We studied 1176 consecutive orbits of attenuation-corrected near surface reflectivity measurements from the TRMM satellite PR instrument. We find that for well-measured statistical moments (orders 0 < q < 2) corresponding to radar reflectivities with dBZ < 57 and probabilities > 10− 6, that the residuals with respect to a pure scaling (power law) variability are remarkably low: ± 6.4% over the range 20,000 km down to 4.3 km. We argue that higher order moments are biased due to inadequately corrected attenuation effects. When a stochastic three — parameter universal multifractal cascade model is used to model both the reflectivity and the minimum detectable signal of the radar (which was about twice the mean), we find that we can explain the same statistics to within ± 4.6% over the same range. The effective outer scale of the variability was found to be 32,000 ± 2000 km. The fact that this is somewhat larger than the planetary scale (20,000 km) is a consequence of the residual variability of precipitation at the planetary scales. With the help of numerical simulations we were able to estimate the three fundamental parameters as α ≈ 1.5, C1 = 0.63 ± 0.02 and H = 0.00 ± 0.01 (the multifractal index, the codimension of the mean and the nonconservation parameter respectively). There was no error estimate on α since although α = 1.5 was roughly the optimum value, this conclusion depended on assumptions about the instrument at both low and high reflectivities. The value H = 0 means that the reflectivity can be modeled as a pure multiplicative process, i.e. that the reflectivity is conserved from scale to scale. We show that by extending the model down to the inner “relaxation scale” where the turbulence and rain decouple (in light rain, typically about 40 cm), that even without an explicit threshold, the model gives quite reasonable predictions about the frequency of occurrence of perceptible precipitation rates.While our basic findings (the scaling, outer scale) are almost exactly as predicted twenty years ago on the basis on ground based radar and the theory of anisotropic (stratified) cascades, they are incompatible with classical turbulence approaches which require at least two isotropic turbulence regimes separated by a meso-scale “gap”. They are also incompatible with classical meteorological phenomenology which identifies morphology with mechanism and breaks up the observed range 4 km–20 000 km into several subranges each dominated by different mechanisms. Finally, since the model specifies the variability over huge ranges, it shows promise for resolving long standing problems in rain measurement from both (typically sparse) rain gage networks and radars.  相似文献   

10.
Aerosol size distributions were measured with Micro Orifice Uniform Deposit Impactor (MOUDI) cascade impactors at the rural Angiola and urban Fresno Supersites in California's San Joaquin Valley during the California Regional PM10/PM2.5 Air Quality Study (CRPAQS) winter campaign from December 15, 2000 to February 3, 2001. PM2.5 filter samples were collected concurrently at both sites with Sequential Filter Samplers (SFS). MOUDI nitrate (NO3−) concentrations reached 66 μg/m3 on January 6, 2001 during the 1000–1600 PST (GMT-8) period. Pair-wise comparisons between PM2.5 MOUDI and SFS concentrations revealed high correlations at the Angiola site (r > 0.93) but more variability (r < 0.85) at the Fresno site for NO3−, sulfate (SO4=), and ammonium (NH4+). Correlations were higher at Fresno (r > 0.87) than at Angiola (r < 0.7) for organic carbon (OC), elemental carbon (EC), and total carbon (TC). NO3− and SO4= size distributions in Fresno were multi-modal and wider than the uni-modal distributions observed at Angiola. Geometric mean diameters (GMD) were smaller for OC and EC than for NO3− and SO4= at both sites. OC and EC were more concentrated on the lowest MOUDI stage (0.056 µm) at Angiola than at Fresno. The NO3− GMD increased from 0.97 to 1.02 µm as the NO3− concentration at Angiola increased from 43 to 66 µg m− 3 during a PM2.5 episode from January 4–7, 2001. There was a direct relationship between GMD and NO3− and SO4= concentrations at Angiola but no such relationships for OC or EC. This demonstrates that secondary aerosol formation increases both concentration and particle size for the rural California environment.  相似文献   

11.
A total of 48 precipitation samples have been collected from individual precipitation events at the Nam Co Monitoring and Research Station for Multisphere Interactions (Nam Co Station, 30°47′N, 90°58′E; 4730 m a.s.l) located in the central Tibetan Plateau from August 2005 to August 2006. All samples were analyzed for major cations (NH4+, Na+, K+, Ca2+ and Mg2+) and anions (Cl−, NO3− and SO42−), conductivity and pH. Precipitation pH values ranged from 6.03 to 7.38 with an average value of 6.59. The high pH is due to large inputs of crustal aerosols in the atmosphere, which contain a large fraction of carbonate. Ca2+ is the dominant cation in precipitation with an average value of 65.58 μeq L− 1 (4.91–301.41 μeq L− 1), accounting for 54% of the total cations in precipitation. HCO3− is the predominant anion, accounting for 62% of the total anions. When compared with data from a snow pit in the Zhadang Glacier 50 km away (5800 m a.s.l), major ion concentration in precipitation at the Nam Co Station is much higher due to local aerosol inputs. Correlation and empirical orthogonal function (EOF) analysis indicate that regional crustal aerosols and species from combustion emissions of residents are the major sources for these ions, lake salt aerosols from the Nam Co nearby and regional mineral aerosols from dry lake sediments are secondary sources, and sea salt contribution is the least due to the long distance transport.  相似文献   

12.
Supercooled drizzle (freezing drizzle) was observed at Inuvik, N.W.T., Canada (68°22′N, 133°42′W) on December 20, 21 and 27, 1995. Meteorological conditions in which the supercooled drizzle could form under low temperatures (colder than −20°C) in the mid-winter season of the Canadian Arctic were examined from the sounding data and data measured by a passive microwave radiometer at ground level. The following results were obtained. (1) Supercooled drizzle fell to the ground with ice pellets and frozen drops on snow crystals. (2) The maximum size of supercooled drizzle particles increased as the depth of cloud layer saturated with respect to water increased. (3) Because a layer of air temperature higher than 0°C was not detected from the sounding data at Inuvik, melting of snow particles was impossible. It was concluded, therefore, that supercooled drizzle was formed by the condensation–coalescence process below freezing temperature.  相似文献   

13.
GPS-synchronized measurements of electric (E) field changes induced by lightning flashes were recorded at six stations in the northeastern verge of the Tibetan Plateau. The height and magnitude of charge neutralized by 65 return strokes, including 16 negative cloud-to-ground (CG) flashes and 2 positive CG flashes, have been fitted with the nonlinear least-square method based on the E field changes of CG flashes observed in a typical thunderstorm with larger-than-usual lower positive charge center (LPCC). Results show that the height of the charge region neutralized by negative CG flashes ranges from 3 km to 5 km above the ground, corresponding to an ambient temperature between − 2 °C and − 15 °C. For the two positive CG flashes, the neutralized charge regions are located at a height of about 5.5 km and the ambient temperature is about − 18 °C, indicating the existence of upper positive charge in the thunderstorm.  相似文献   

14.
The concentrations of submicron aerosols in the size range 10−7 to 10−5 cm, also called Aitken nuclei (AN) were measured over the Indian Ocean enroute India-Antarctica-India within the 10°E–70°E longitude zone from about 10°N to 70°S latitude on board MV Thuleland during the period from November 26, 1986 to March 18, 1987 as part of the scientific activities on the Sixth Indian Antarctic Expedition. Our analyses showed that only in about 25% of the cases, AN count fell below 1000 cm−3. Throughout the tropical trade wind region, the concentrations of AN were relatively stable with an average of about 3000 cm−3 (medians of 2600 and 1700 cm−3 in Northern and Southern Hemispheres, respectively). Large AN concentrations were found to be associated with higher sea surface temperatures and stronger surface winds in this region. In contrast, the scatter of single observations was found to be remarkable over South Indian Ocean and in Antarctic waters. The average AN concentration over the Indian Ocean to the south of 30°S was of the order of 1500 cm−3. No definite correlation could be established between large AN concentration and sea surface temperature, wind speed or wave height. Period with very low concentrations were, however, associated with clear sky conditions and calm winds or light breeze. Many events of sudden short-lived but large increase in AN concentrations were observed over the south Indian Ocean and in Antarctic waters and these were always associated with the approach of frontal systems. It is likely that particle production by bursting bubbles and sea spray as well as photochemical reactions and gas-to-particle conversions play important role in the observed high concentration of AN over South Indian Ocean.  相似文献   

15.
In this paper warm cloud microphysical parameters including cloud droplet number concentration (Nc), liquid water content (ql) and effective radius (re) from 75 flights around the Beijing area during 2005 and 2006 are summarized. Average Nc (cm− 3) for Cu, Sc, Ac, As and Ns are 376 ± 290, 257 ± 226, 147 ± 112, 60 ± 35 and 60 ± 84, respectively. Many records of high Nc above 1000 cm− 3 are observed. The large standard deviations indicate a large variation of Nc and ql in this region. The maxima of ql reach 1.4 g m− 3 in Cu and 1.0 g m− 3 in Sc, respectively. Different parameterizations of effective radius are examined with the in-situ data in this area. There are different ways to obtain the prefactor representing the relationship between effective radius and mean volume radius. Significant systematic errors are found to be at the large sizes when the prefactor is expressed with relative dispersion under the Gamma Distribution. Fixed prefactor of 1, which was widely used, even produces much larger error. A prefactor of 1.22 is found to be better than the former two methods by fitting with the observed data. The effective radius is further parameterized as functions of mean volume radius, liquid water content and cloud droplet number concentration. We suggest that the effective radius can be parameterized as re,p ≈ 1.20rv + 0.22–1.28/rv2, which is a practical and more accurate scheme without too much computation complexity.  相似文献   

16.
Black carbon relationships with emissions and meteorology in Xi'an, China   总被引：4，自引：0，他引：4  
Aerosol black carbon (BC) was measured every 5 min at Xi'an, China from September 2003 to August 2005. Daily BC concentrations ranged from 2 to 65 μg m− 3, averaging 14.7 ± 9.5 μg m− 3 and displayed clear summer minima and winter maxima. BC typically peaked between 0800 and 1000 LST and again between 2000 and 2200 LST, corresponding with morning and evening traffic combined with nighttime residential cooking and heating. The nocturnal peak was especially evident in winter, when more domestic heating is used and pollutant-trapping surface-inversions form earlier than in summer. BC frequency distributions the most commonly occurring concentrations occurred between 5 and 10 μg m− 3 in all four seasons. BC ranged from 1.6% and 15.6%, and averaged 8.3% of PM2.5. A clear inverse relationship between BC and wind speed (WS) was found when WS was below 2.5 to 3.0 m s− 1, implying a local origin for BC. Mixed layer depths (MLDs) were shallower during BC episodes compared to cleaner conditions.  相似文献   

17.
In the present study, the precipitation near Büyükçekmece Lake, which is one of the important drinking water sources of Istanbul city, was studied during October 2001–July 2002. Seventy-nine bulk precipitation samples were collected at two sampling stations near the Lake (41°2′35″N, 28°35′25″E and 41°5′30″N, 28°37′7″E). The study comprised the determination of H+, Cl−, NO3−, SO42−, NH4+, Na, K, Mg, Ca, Al, Ba, Fe, Cu and Mn concentrations in bulk deposition rain event samples. The average volume-weighted pH value was found to be 4.81, which points out that the rain is slightly acidic. High sulfate concentrations were observed together with high H+ ion values. Sulfur emissions were the major cause for the observed high hydrogen ion levels. On the basis of factor analysis and correlation matrix analysis, it has been found that in this region, acid neutralization is brought about by calcium rather than the ammonium ion. The varimax rotated factor analysis grouped the variables into four factors, which are crustal, marine and two anthropogenic sources.  相似文献   

18.
Summary Crystal size and optical depth of optically thin cirrus clouds and contrails over the North Sea and Adriatic Sea on the 18th of October 1989 are retrieved by comparison of NOAA AVHRR/2 brightness temperatures of channel 4 (9.97 µm–11.56 µm) and channel 5 (11.075 µm–12.76 µm) with one dimensional radiative transfer calculations. Measured brightness temperatures in all three infrared channels and their differences show higher values for contrails than for cirrus. The radiative properties of young contrails are consistent only, if smaller crystal size than those given for natural cirrus are adopted for the calculations. However, there is a continuous transition in radiative parameters between clouds classified as natural cirrus or contrails. For the test areas ice clouds are classified with respect to optical depth and mean crystal size. Finally infrared fluxes and heating rates in the spectral range 4 µm–40 µm are calculated for an atmosphere with a 500 m thick contrail or cirrus uncinus. At given ice content a far stronger atmospheric warming is found for a contrail with relatively small ice crystals: up to 80 K/day at cloud base for an ice content of 0.05 gm–3 compared to 10 K/day for a cirrus uncinus with large crystals.With 11 Figures  相似文献   

19.
To further investigate the influence of cloud base temperature, updraft velocity and precipitation particle constitution on cloud electrification, five thunderstorms in various regions of China were simulated by using the three-dimensional compressible hailstorm numerical model including inductive and non-inductive charging mechanisms. The results indicate that changes of cloud base temperature have an influence on the initial electrification. Comparison of the above cases shows that in the case of warm cloud base and moderate updraft velocity (< 20 m s−  1), active electrification occurred below the − 10 °C level before moving upward to the − 20 °C level. In contrast, when cloud base is cold and updraft velocity is intensive, the main charging region is at the − 20 °C or even higher level. In that case, the vertical extent of the main negative charge region becomes larger with the increase of cloud base temperature. Apart from the main dipolar or tripolar charge structure, some smaller charge regions with relatively high values of charge density may also appear. Frozen drops, originating mainly from supercooled raindrops, mainly get electrified through charging interactions with snow at or below the − 20 °C level. They are responsible for the negative charge region near the melting level at the initial stage of precipitation if there is a large supercooled raindrop content. Non-inductive charging during hail-snow collisions is rather weak, resulting in the charge density on hail of no more than − 0.01 nC m− 3.  相似文献   

20.
A large data set of the total (liquid and ice) cloud water content in continental stratiform clouds of middle latitudes was collected in the Cloud Physics Laboratory (CPL) of the Central Aerological Observatory (CAO). The total flight length in clouds was over 100,000 km. On the basis of these data, the cumulative frequencies of TCWC occurrences F(w) were found and parameterized by log-normal distributions which parameters depend on temperature. In the temperature interval from 0°C to −40°C the empirical values of F(w) deviate of no more than 5% from the parameterized ones.The new data, with a better probe detecting threshold, lead to a noticeable increase of the cases with small values of cloud water content and correspondingly, decrease of cloud water content characteristic values comparing with the values previously obtained by many authors. The difference increased with decreasing temperature.  相似文献   

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