Observation of the temperature structure function parameter,C T 2, over the ocean

Shipboard measurements of temperature fluctuations, mean wind, temperature, and humidity permit comparisons to be made of experimental and empirical estimates of c_t ², the temperature structure function parameter. Surface flux estimates are obtained from bulk aerodynamic formulae. Temperature fluctuation data are selected to minimize a salt-contamination effect which causes increases in temperature variance. Predictions for C_T ² based on surface flux scaling agree within 20%, except for near neutral and large unstable conditions where disagreement can be attributed to measurement problems.     

Characteristics of the Lyman-alpha humidiometer and measurements of turbulent humidity fluctuations over the ocean

The characteristics of a Lyman-alpha humidiometer have been carefully examined in an air-conditioned test chamber. The results confirm that when carefully used, this humidiometer is suitable for measurements of turbulent humidity fluctuations. Measurements with a Lyman-alpha humidiometer were carried out in the surface boundary layer over the ocean. The relation between turbulent intensity ( _a = a ^ov2) and the friction humidity (a _*) can be expressed as _a = l.6a _*. The spectrum of turbulent humidity for wind speeds larger than 3 m s ^–1 conforms to the similarity law in the surface boundary layer. The spectrum has two characteristic normalized frequencies, namely, a higher peak and a secondary peak (or a shoulder).     

Measurements of the rate of dissipation of turbulent kinetic energy, ɛ, over the ocean

In a series of cruises during the last three years, the Naval Postgraduate School Environmental Physics Group has made more than 1000 shipboard measurements of the rate of dissipation of turbulent kinetic energy, , using inertial subrange (high frequency) techniques. Utilizing the bulk-aerodynamic method to obtain the relevant Monin-Obukhov surface layer scaling parameters, the overwater dimensionless dissipation function 321-01, has been examined with unprecedented statistical certainty. The results agree well with those of Wyngaard and Coté (1971) for the stable case but they agree more closely with the parameterization of McBean and Elliott (1975) for unstable conditions. Drag coefficients computed from the data are in good agreement with the curve given by Garratt (1977).     

Temperature and humidity structure of the sub-cloud layer over land

Observations of temperature, pressure and humidity have been made from an aircraft beneath cumulus clouds which formed over extensive flat country. In fair weather over land, cumulus cloud base is generally above the average top of the well-mixed convection layer so that penetrative convection is necessary to initiate cloud formation. The convective layer does not evolve and deepen uniformly over large areas (say greater than 100-km radius). Rather, it develops a patchy structure at 1–10 km scales. Such patches, close beneath cloud base, have thermodynamic properties very like those of the convection layer and in such regions that layer effectively extends right up to cloud base. Meso-scale effects (e.g., 50 km) seem to be important in determining where clear and cloudy areas occur, and although it appears reasonable to attribute this to local dynamic effects (e.g., subsidence), it is not possible to eliminate other possibilities on the basis of the present data.     

Measurements of H2S and SO2 over the Atlantic Ocean

Concentrations of sulfur gases H₂S and SO₂ have been measured in the marine atmosphere over the Atlantic Ocean at various sites. Mean values of 40 ng H₂S m^-3 STP and 209 ng SO₂ m^-3 STP are the results of the measurements. A diurnal variation of H₂S concentration was detected on the west coast of Ireland with nighttime concentrations of up to 200 ng H₂S m^-3 STP and values below detection limit (15 ng H₂S m^-3 STP) during daytime.     

Water-Soluble dicarboxylic acids, ketoacids and dicarbonyls in the atmospheric aerosols over the southern ocean and western pacific ocean

Water-soluble dicarboxylic acids (DCAs), ketoacids, and α-dicarbonyls in the marine aerosol samples collected over the Southern Ocean and western Pacific Ocean were determined. Oxalic acid was the most abundant species, followed by malonic acid and then succinic acid. It is suggested that aerosol concentrations of the organics over the Southern Ocean in this work represent their global background levels. Over the Southern Ocean, total concentrations of DCAs ranged from 2.9 to 7.2 ng m⁻³ (average: 4.5 ng m⁻³), ketoacids from 0.14 to 0.40 ng m⁻³ (av.: 0.28 ng m⁻³), and dicarbonyls from 0.06 to 0.29 ng m⁻³ (av.: 0.11 ng m⁻³). Over the western Pacific, total concentrations of DCAs ranged from 1.7 to 170 ng m⁻³ (av.: 60 ng m⁻³), ketoacids from 0.08 to 5.3 ng m⁻³ (av.: 1.8 ng m⁻³), and dicarbonyls from 0.03 to 4.6 ng m⁻³ (av.: 0.95 ng m⁻³). DCAs over the western Pacific have constituted a large fraction of organic aerosols with a mean DCAs-C/TC (total carbon) of 7.0% (range: 0.59–14%). Such a high value was in contrast to the low DCAs-C/TC (av.: 1.8%; range: 0.89–4.0%) for the Southern Ocean aerosols. Based on the relative abundances and latitudinal distributions of these organics, we propose that long-range atmospheric transport is more important over the western Pacific Ocean, in contrast, in situ photochemical production is more significant over the Southern Ocean although absolute concentrations of the organics are much lower.     

Kolmogorov constants for CO2, wind velocity,air temperature,and humidity fluctuations over a crop surface

The Kolmogorov constants for CO₂, wind velocity, air temperature, and humidity fluctuations were evaluated from measurements made over soybean and grain sorghum fields and found to be 0.78 ± 0.11, 0.49 ± 0.08, 0.70 ± 0.15, and 0.99 ± 0.16, respectively. These results are consistent with recent observations reported in the literature.Published as Paper No. 7255, Journal Series, Nebraska Agricultural Experiment Station. The work reported here was conducted under Regional Research Project 11-33 and Nebraska Agricultural Experiment Station Project 27-003.Associate Professor and Post Doctoral Research Associate, respectively, Center for Agricultural Meteorology and Climatology, Institute of Agriculture and Natural Resources, University of Nebraska, Lincoln, NE, U.S.A., 68583-0728.     

Correlations between velocity temperature and humidity fluctuations in the air above land and ocean

Observations made over land and ocean show that the structure of convection in the lowest one-third of a well-mixed layer may be studied in terms of a density-related variable (e.g., _v ) without regard to whether structural elements are ascending or descending. This no longer holds in the remainder of the layer. Further, the temperature-humidity correlation is generally not the same for ascending and descending elements in any part of the layer. The consequences for short-path optical propagation are considered.     

On the measurement of vertical humidity transport over land

Humidity fluctuations over land were measured by a Ly- humidiometer and dew point hygrometer; the results showed excellent agreement. From simultaneous measurements of vertical velocity, temperature, and downwind velocity, the universal shape of the spectra and cospectra for humidity transport were examined, and compared with those for heat and momentum.     

An investigation of the Iranian climatic changes by considering the precipitation, temperature, and relative humidity parameters

The present study tends to describe the survey of climatic changes in the case of the eastern and central areas of Iran and, to some extent, the northern parts. The monthly and yearly change trends in the minimum, maximum and mean temperatures, relative humidity, and the precipitation were surveyed for 26 synoptic stations in Iran during a 55-year period. The study was carried out by using the ??-Kendall test. The results showed the same temperature changes for the centrally located stations as the eastern and northern ones. Most of the stations in Zagros showed no significant temperature changes. A significant decrease in the precipitation was seen in summer in different stations. Most of the eastern and centrally located stations showed a decrease in relative humidity trend, while this condition was not recorded in Zagros and northern part of Iran. The present results also showed that the upward trend of minimum air temperature had an effect in increasing the mean air temperature in the stations with temperature ascending trend. This effect of minimum temperature was significantly more than that of the maximum temperature, which could be the result of increasing the amount of greenhouse gases and the reflection of received thermal energies, from land through the night. This increase in the temperature and a decrease in relative humidity would cause an increase in the evaporation of the received precipitation.     

Large-sample estimates of wind fluctuations over the ocean

The best quality wind data from the Norwegian sector of the North Sea, consisting of 3662 20-min time series measured at the top of the Statfjord A drilling derrick, are analyzed. Identification of Autoregressive wind models with Akaike's AIC and Achwarz's BIC measures appears to give rather arbitrary results. Spectral estimation with FFT- and AIC-identified AR-methods give almost identical results in the mean. At the higher frequencies (% MathType!MTEF!2!1!+-% feaafeart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamOzaaaa!36D7!\[f\] > 10^–2 s^–1) the spectrum is estimated to follow the usual inertial subrange law with little variability. The small-scale turbulent intensity is estimated to be very low, even in hurricane conditions. Comparatively, the low-frequency (% MathType!MTEF!2!1!+-% feaafeart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamOzaaaa!36D7!\[f\] ~ 10^–3 s^–1) fluctuations are more energetic than expected. None of the chosen low-frequency characteristica appear to be significantly linearly correlated to the available mean weather variables. However, some nonlinear relations appear to exist.     

On the onset of entrainment instability over the ocean

The marine atmospheric boundary layer is characterized by cool temperatures and high humidity. Clouds are observed over most of the oceans. It is generally accepted that these overcast cloud decks break up into scattered fragments due to cloud-top entrainment instability. That is, if the air above the boundary layer is sufficiently cool and dry relative to cloud top, the buoyancy flux will be directed upwards and entrainment can occur freely.A boundary-layer model is used to test the sensitivity of the model atmosphere to the various processes which promote the onset of cloud-top entrainment instability. It is found that the transition from a solid cloud deck to scattered cumulus clouds depends on a rate process. The cloud cover is sensitive to mesoscale variations in sea surface temperature only if the cloud-top inversion is sufficiently weak.     

Eddy flux measurements over the ocean and related transfer coefficients

Eddy correlation measurements of vertical turbulent fluxes made during AMTEX 1975 are used to assess the reliability of flux prediction from established bulk transfer relations, using both surface-layer and planetary boundary-layer formulations. The surface-layer formulae predict momentum and latent heat fluxes to an accuracy comparable to the direct eddy correlation method, using transfer coefficients of C _DN (at 10m and in neutral conditions) increasing with wind speed, and a constant C _EN - 1.5 × 10 ^–3 . The data suggest C _CHN , for sensible heat, increases significantly with wind speed and is on average 30% lower than C _CEN The boundary-layer drag coefficient, C _GD , agrees within about 40% of recently published values using a vertically averaged geostrophic wind to the height of the lowest temperature inversion, corrected for trajectory curvature. Values of _* / from which C _CGH is derived, are in excellent agreement if the published values are modified to account for inappropriate surface temperatures used in their derivation. Preliminary values of C _GE are also presented.     

Measurements of the turbulent heat flux over the sea

The turbulent heat flux was measured with two instruments simultaneously over the Baltic Sea by means of the eddy-correlation method. In one observational period, a small but noticeable divergence in heat flux was found, which may be explained by the advection of colder air. The parameterization of heat flux by the bulk method leads to a value for C _Hof 1 × 10^–3.     

The estimation of the surface-layer parameters from wind velocity,temperature and humidity profiles by least-squares methods

The estimation of the surface-layer parameters u _* (friction velocity), _* and q _* (temperature and humidity scales), _r and q _r (temperature and humidity reference values), z _o (roughness length) and d (zero-displacement) from vertical profiles of wind velocity, temperature and humidity by least-squares methods is described. The estimation is based on the flux-gradient relationships and the constant flux assumption for the transfer of momentum, sensible heat and matter near the Earth's surface.Test calculations were carried out with the vertical profile data from the GREIV I 1974 experiment and the Great Plains Turbulence Project.     

Measurements and Parametrizations of the Atmospheric Boundary-Layer Height at Dome C,Antarctica

An experimental campaign, Study of the Atmospheric Boundary Layer Environmental at Dome C, was held during 2005 at the French-Italian station of Concordia at Dome C. Ground-based remote sensors, as well as in situ instrumentation, were used during the experimental campaign. The measurements allowed the direct estimation of the polar atmospheric boundary-layer height and the test of several parametrizations for the unstable and stable boundary layers. During the months of January and February, weak convection was observed while, during the polar night, a long-lived stable boundary layer occurred continuously. Under unstable stratification the mixing-layer height was determined using the sodar backscattered echoes and potential temperature profiles. The two estimations are highly correlated, with the mixing height ranging between 30 and 350 m. A simple prognostic one-dimensional model was used to estimate the convective mixing-layer height, with the correlation coefficient between observations and model results being 0.66. The boundary-layer height under stable conditions was estimated from radiosounding profiles as the height where the critical Richardson number is reached; values between 10 and 150 m were found. A visual inspection of potential temperature profiles was also used as further confirmation of the experimental height; the results of the two methods are in good agreement. Six parametrizations from the literature for the stable boundary-layer height were tested. Only the parametrization that considers the long-lived stable boundary layer and takes into account the interaction of the stable layer with the free atmosphere is in agreement with the observations.     

Small-scale atmospheric structure deduced from measurements of temperature,humidity and refractive index

Measurements have been made with fast-response multi-channel temperature, humidity and refractive index sensors flown to 2000 m on a tethered balloon to investigate small-scale fluctuations important in radio-wave scattering, their relation to atmospheric parameters, and their spatial variation in both one and three dimensions. Data from the three types of sensors at one point were consistent for frequencies up to about 8 Hz. Power spectra of data at various heights were computed over 0.1 to 10 Hz and generally showed slopes (on a log-log plot) close to - 5/3 above 1 Hz but ranged from –1.5 to – 3.5 at lower frequencies; in this range (f < 1 Hz) slopes were close to – 5/3 for negative Richardson number (Ri), provided temperature gradients were steeper than –1.1 °C 100 m^–1 and wind shears > 1.4 x 10^–2 s^–1 approx. Steeper slopes were generally associated with stable atmospheric conditions but no precise relation to the above parameters was found. Spectral density was a maximum for Ri –0.75.Cross-correlations of 0.5 were frequently observed between sensors 1 m apart in orthogonal directions; in the vertical, examples of negative correlation of vapour pressure were occasionally found over this spacing. Using four sensors spaced in line over 9 m, cross-spectrum phase calculations of drift speeds were found to be consistent with measured wind speeds. The ratio of identification distance (coherence=0.6) to scale size of irregularities ranged from 0.25 to 0.5 with no apparent relation to height or meteorological parameters.     

长江下游农业生态区CO2通量的观测试验

利用2001年6月10日~7月20日在安徽省全椒县稻田和2002年6月10日~7月20日在肥西县农作物混作区观测的近地层CO₂和能量通量资料，对农作物混作区和稻田CO₂通量特征进行了比较。结果表明:平均情况下，观测期内稻田白天(夜间)吸收(放出) CO₂为55.16 g·m-2(14.19 g·m-2)；农作物混作区白天(夜间)吸收(放出) C02为22.67 g·m”(12.40 g·m-2)；稻田白天吸收的CO₂通量随水稻生长而逐渐增加，夜间放出的CO₂在拔节期最高；农作物混作区CO₂通量在整个观测期并没有显著改变；稻田和农作物混作区均为大气CO₂的汇。对CO₂通量与光合有效辐射的关系分析表明:白天稻田吸收的CO₂通量与到达地面的光合有效辐射存在着显著的负相关关系。文中结果为数值模拟稻田与近地层大气CO₂交换提供了重要依据。     

Evidence of the terdiurnal,S 3, atmospheric tide in the surface wind field over the ocean

Surface winds were measured from anchored buoys at the corners of a 100-km triangle in the Atlantic ocean for three weeks in September 1972. The measurements were part of the British Royal Society Joint Air-Sea Interaction Project, JASIN-72. Peaks were found at a frequency of 0.125 cph (8-h period) in various wind statistics, indicating the presence of the terdiurnal, S ₃, component of the atmospheric tides that had previously been extensively studied because it is a prominent component in surface air-pressure records.     

Global ocean circulation and equator-pole heat transport as a function of ocean GCM resolution

To determine whether resolution of smaller scales is necessary to simulate large-scale ocean climate correctly, I examine results from a global ocean GCM run with different horizontal grid spacings. The horizontal grid spacings span a range from coarse resolutions traditionally used in climate modeling to nearly the highest resolution attained with today's computers. The experiments include four cases employing 4°, 2°, 1° and 1/2° spacing in latitude and longitude, which were run with minimal differences among them, i.e., in a controlled experiment. Two additional cases, 1/2° spacing with a more scale-selective sub-gridscale mixing of heat and momentum, and approximate 1/2° spacing, are also included. The 1/2° run resolves most of the observed mesoscale eddy energy in the ocean. Artificial constraints on the model tend to minimize differences among the different resolution cases. Nevertheless, the simulations show significant changes as resolution increases. These changes generally but not always bring the model into better agreement with observations. Differences are typically more noticeable when comparing the 4° and 2° runs than when comparing the 2° and 1° runs or the 1° and 1/2° runs. A reasonable conclusion to draw for current studies with coupled ocean-atmosphere GCMs is that the ocean grid spacing could be set to about 1° to accrue the benefits of enhanced resolution without paying an excessively steep price in computer-time cost. The model's poleward heat transport at 1/2° grid spacing peaks at about 1 × 10¹⁵ W in the Northern Hemisphere and 0.5 × 10¹⁵ W in the Southern Hemisphere. These values are significantly below observations, a problem typical of ocean GCMs even when they are less constrained than in the present study. This present problem is alleviated somewhat in the 1/2° run. In this case, however, the eddies resolved by the model generally act to counter rather than to reinforce the heat transport of the mean flow. Improved heat transport may result less from enhanced resolution than from other changes made in this version of the model, such as more accurate wind forcing.