Variation Of Lapse Rate Research Articles

Distinguishing Time Scales of Katabatic Flow in Complex Terrain

To examine spatial and temporal scales of katabatic flow, a distributed temperature sensing (DTS) optical fiber was deployed 2 km down a mild slope irregularly interrupted by small-scale drainage features as part of the Mountain Terrain Atmospheric Modeling and Observation (MATERHORN) experiment conducted at the U.S. Army Dugway Proving Ground, Utah. The fiber was suspended at two heights near the surface, enabling measurement of variations in lapse rate near the surface at meter-scale spatial resolution with 1-min temporal resolution. Experimental results derived from the DTS and tower-mounted instrumentation indicate that airflow through small-scale drainage features regulated the local cooling rate whereas topographic slope and distance along the drainage strongly influenced the larger-scale cooling rate. Empirical results indicate that local cooling rate decays exponentially after local sunset and basin-wide cooling rate decreases linearly with time. The difference in the functional form for cooling rate between local and basin-wide scales suggests that small-scale features have faster timescales that manifests most strongly shortly after local sunset. More generally, partitioning drainage flow by scale provides insight and a methodology for improved understanding of drainage flow in complex terrain.

Air temperature and lapse rate variation in the ice‐free and glaciated areas of northern James Ross Island, Antarctic Peninsula, during 2013–2016

Studies assessing air temperature variations and their dependence on altitude from the eastern side of the Antarctic Peninsula are sparse. In this paper, we analyse air temperature and near‐surface lapse rates from the Ulu Peninsula (James Ross Island, Antarctic Peninsula). The temperature data were acquired from nine sites both in ice‐free areas and glaciers of the Ulu Peninsula in 2013–2016. The most important factors influencing air temperature differences were sea‐ice conditions, topography and ground surface properties. During the study period, air temperature decreased with height with the mean lapse rate of 0.40 °C 100 m−1 for the ice‐free sites (10–375 m a.s.l.) and 0.43 °C 100 m−1 for the glaciated sites (268–539 m a.s.l.). However, the values were lower in winter (ice‐free: 0.02 °C 100 m−1 and glacier: 0.31 °C 100 m−1) than in summer (ice‐free: 0.62 °C 100 m−1 and glacier: 0.51 °C 100 m−1) for both categories. The air layer between 10 and 56 m a.s.l. in the ice‐free area revealed an almost year‐round air temperature inversion resulting in a mean lapse rate of −0.79 °C 100 m−1 and an air temperature inversion frequency reaching up to 43%. The temperature inversion frequency was 10% lower for the lowest air layer for the glacier category, which was between 268 and 356 m a.s.l. The land surface air temperature was the highest when the wind was from the northwest and lowest when it was from the south–southwest. The near‐surface lapse rate–wind direction relationship was the most pronounced for the air layer between 10 and 56 m a.s.l. with the lowest mean lapse rate for west–southwest wind (−2.83 °C 100 m−1) and the highest for east–northeast wind (0.41 °C 100 m−1).

Assessing seasonal variation of near surface air temperature lapse rate across India

ABSTRACTPrecise characterization of surface air temperature at different spatial scales remains a challenge as it often requires a dense network of temperature sensors. The most common approach for estimating surface air temperature at a desired location in hydrological and terrestrial models is to interpolate surface air temperature observations obtained from a sparse set‐up of temperature sensors using the global standard uniform lapse rate. This interpolation technique, though easy to use, can lead to unreliable results, as the global standard uniform lapse rate may not be representative of seasonal and local variations in lapse rate. In this study, linear and nonlinear regression relationships are derived to estimate mean minimum, mean and mean maximum near surface air temperatures (at monthly and annual time scales) across India. The normal daily air temperature data from 439 stations and their corresponding latitude, longitude and elevation are used in the analysis. The computed temperature gradients exhibit seasonal variation. The effects of elevation and longitude are more pronounced in pre‐monsoon (March–May) and post‐monsoon (October–November) months, whereas the effects of latitude are more in winter months (December–February). Results indicate that the global standard uniform lapse rate (− 0.65 ° C 100 m− 1) is only applicable for monthly mean maximum temperature for April and May. The highest interpolation reliability is obtained for monthly mean minimum temperature. The regression equations though simple, hold promise for describing surface air temperature across India.

Combining thin-plate spline interpolation with a lapse rate model to produce daily air temperature estimates in a data-sparse alpine catchment

Insufficient availability of weather stations recording air temperature is a common problem in many alpine regions. The low station density combined with the high variability of air temperature means that interpolated fields based on simple or more complex interpolation techniques are unlikely to be representative of the real patterns of air temperature. In this study, a novel method was developed to tackle this problem, following initial investigation of lapse rate variability in the study domain: the alpine Clutha catchment, New Zealand. Owing to a series of complexities in lapse rate variability, a multi-layer approach was adopted to produce 1 km2 daily fields of maximum (Tmax) and minimum air temperature (Tmin). The first layer of the Tmax and Tmin models was calculated using a trivariate thin-plate spline, which was constrained to the elevations of the continuous network to avoid unrealistic extrapolation. To compensate for missing continuous high elevation records, two lapse rate models were implemented to scale air temperature above the first layer. The two lapse rate models were based on the dominant processes driving lapse rate variation, which were found to be cold air ponding (Tmin) and spatial differences in relative humidity (Tmax). Independent station records were used to assess accuracy and compare the resultant fields to an existing product (the Virtual Climate Station Network) and a more conventional method based on a bivariate spline and a constant lapse rate. The validation revealed that the new methods developed here have led to a substantial improvement in producing spatial estimates of Tmax, with a mean root mean square error (RMSE) of 2.38 °C, while progress in regard to Tmin was more limited (mean RMSE of 2.93 °C). As such, this work demonstrates that inclusion of the driving processes controlling lapse rates in interpolation routines can lead to improvements in accuracy.

Near‐surface air temperature lapse rates in the mainland China during 1962–2011

Land surface hydrological modeling is sensitive to near‐surface air temperature, which is especially true for the cryosphere. The lapse rate of near‐surface air temperature is a critical parameter when interpolating air temperature from station data to gridded cells. To obtain spatially distributed, fine‐resolution near‐surface (2 m) air temperature in the mainland China, monthly air temperature from 553 Chinese national meteorological stations (with continuous data from 1962 to 2011) are divided into 24 regional groups to analyze spatiotemporal variations of lapse rate in relation to surface air temperature and relative humidity. The results are as follows: (1) Evaluation of estimated lapse rate shows that the estimates are reasonable and useful for temperature‐related analyses and modeling studies. (2) Lapse rates generally have a banded spatial distribution from southeast to northwest, with relatively large values on the Tibetan Plateau and in northeast China. The greatest spatial variability is in winter with a range of 0.3°C–0.9°C · 100 m−1, accompanied by an inversion phenomenon in the northern Xinjiang Province. In addition, the lapse rates show a clear seasonal cycle. (3) The lapse rates maintain a consistently positive correlation with temperature in all seasons, and these correlations are more prevalent in the north and east. The lapse rates exhibit a negative relationship with relative humidity in all seasons, especially in the east. (4) Substantial regional differences in temporal lapse rate trends over the study period are identified. Increasing lapse rates are more pronounced in northern China, and decreasing trends are found in southwest China, which are more notable in winter. An overall increase of air temperature and regional variation of relative humidity together influenced the change of lapse rate.

A Comparison of Methods for Filling Gaps in Hourly Near-Surface Air Temperature Data

AbstractNear-surface air temperature observations often have periods of missing data, and many applications using these datasets require filling in all missing periods. Multiple methods are available to fill missing data, but the comparative accuracy of these approaches has not been assessed. In this comparative study, five techniques were used to fill in missing temperature data: spatiotemporal correlations in the form of empirical orthogonal functions (EOFs), time series diurnal interpolation, and three variations of lapse rate–based filling. The method validation used sets of hourly surface temperature observations in complex terrain from five regions. The most accurate method for filling missing data depended on the number of available stations and the number of hours of missing data. Spatiotemporal correlations using EOF reconstruction were most accurate provided that at least 16 stations were available. Temporal interpolation was the most accurate method when only one or two stations were available or for 1-h gaps. Lapse rate–based filling was most accurate for intermediate numbers of stations. The accuracy of the lapse rate and EOF methods was found to be sensitive to the vertical separation of stations and the degree of correlation between them, which also explained some of the regional differences in performance. Horizontal distance was less significantly correlated with method performance. From these findings, guidelines are presented for choosing a filling method based on the duration of the missing data and the number of stations.

A simple height-based correction for temperature downscaling in complex terrain

A new downscaling method has been developed to improve forecasts of near-surface temperature. This involves applying a correction to forecast temperatures to account for the difference in height between the terrain in the forecast model and the real terrain, using an estimate of the lapse rate of temperature. The strongest variations in lapse rate are found to occur overnight, being a function of cloud cover and geostrophic wind speed. These variables similarly influence the night time lapse rate in the UK Met Office Unified Model forecast at 4 km resolution. Therefore, a simple algorithm has been employed to estimate the lapse rate at a given location, based on forecast model temperature and elevation fields. The algorithm has a positive impact on performance in stable conditions, compared to assuming an adiabatic lapse rate at all times. © Crown Copyright 2010. Reproduced with the permission of the Controller of HMSO. Published by John Wiley & Sons, Ltd

Snowmelt runoff modelling in an arid mountain watershed, Tarim Basin, China

AbstractThe feasibility of simulating daily snowmelt runoff in an arid mountain watershed with limited hydro‐meteorological measurements was explored with an enhanced temperature‐index snowmelt runoff model (SRM) in which the degree‐day factor (DDF) is varied on the basis of shortwave solar radiation and snow albedo. The model satisfactorily simulated snowmelt runoff with a model efficiency of 0·64 for the calibration year and efficiency values of 0·78 and 0·51 for two validation years. Analysis indicated that the model was sensitive to lapse rate and snow albedo parameterization. The distinct seasonal variation of lapse rate played a key role for successful simulation. Snow albedo parameterization, which directly scaled snow cover percentage into snow albedo, worked quite well for the watershed although further validation is needed. Eight‐day snow cover data from the Moderate Resolution Imaging Spectroradiometer (MODIS) were used to feed the model. A frequency filter, which filtered out the clouds and large fluctuation of snow cover from the MODIS snow cover data, also improved model performance. The model, however, did not simulate peak stream flows well as most of the model runs underestimated them. Copyright © 2008 John Wiley & Sons, Ltd.

Relationships between Stability and Monsoon Convection

Abstract Rawinsonde data from the Australian Monsoon Experiment are analyzed to determine the manner in which the atmospheric stratification of density and moisture respond to large amounts of convective latent heat release. The study focuses on time series of data from a ship located at the northern end of the Gulf of Carpentaria during active and break periods of the monsoon. Variations in lapse rate or vertical stratification through the depth of the troposphere are found to occur mainly between active and break periods, rather than on a day-to-day basis. This is interpreted as being due to midtropospheric temperature being adjusted by dynamical processes over large scales rather than in situ response to localized convection. Between active and break periods large changes occurred in midtropospheric moisture. Variations in convective activity are well related to variations in lower and middle tropospheric moisture content. The break coincided with a drying due to large-scale horizontal advection. Conve...

Non-linear climate feedback analysis in an atmospheric general circulation model

A method is described for evaluating the ‘partial derivatives’ of globally averaged top-of-atmosphere (TOA) radiation changes with respect to basic climate model physical parameters. This method is used to analyse feedbacks in the Australian Bureau of Meteorology Research Centre general circulation model. The parameters considered are surface temperature, water vapour, lapse rate and cloud cover. The climate forcing which produces the changes is a globally uniform sea surface temperature (SST) perturbation. The first and second order differentials of model parameters with respect to the forcing (i.e. SST changes) are estimated from quadratic least square fitting. Except for total cloud cover, variables are found to be strong functions of global SST. Strongly non-linear variations of lapse rate and high cloud amount and height appear to relate to the non-linear response in penetrative convection. Globally averaged TOA radiation differentials with respect to model parameters are also evaluated. With the exception of total cloud contributions, a high correlation is generally found to exist, on the global mean level, between TOA radiation and the respective parameter perturbations. The largest non-linear terms contributing to radiative changes are those due to lapse rate and high cloud. The contributions of linear and non-linear terms to the overall radiative response from a 4 K SST perturbation are assessed. Significant non-linear responses are found to be associated with lapse rate, water vapour and cloud changes. Although the exact magnitude of these responses is likely to be a function of the particular model as well as the imposed SST perturbation pattern, the present experiments flag these as processes which cannot properly be understood from linear theory in the evaluation of climate change sensitivity.

Parameterizations of cloud feedback in a radiative-convective model

The effect of cloud feedback on the response of a radiative-convective model to a change in cloud model parameters, atmospheric CO2 concentration, and solar constant has been studied using two different parameterization schemes. The method for simulating the vertical distribution of both cloud cover and cloud optical thickness, which depends on the relative humidity and on the saturation mixing ratio of water vapor, respectively, is the same in both approaches, but the schemes differ with respect to modeling the water vapor profile. In scheme I atmospheric water vapor is coupled to surface parameters, while in scheme II an explicit balance equation for water vapor in the individual atmospheric layers is used. For both models the combined effect of feedbacks due to variations in lapse rate, cloud cover, and cloud optical thickness results in different relationships between changes in surface temperature, planetary temperature, and cloud cover. Specifically, for a CO2 doubling and a 2% increase in solar constant, in both models the surface warming is reduced by cloud feedback, in contrast to no feedback, with the greater reduction in scheme I as compared to that of scheme II.

Climatic Relationships of Permafrost Zones in Areas of Low Winter Snow-Cover

In areas with under 50 cm snow cover in winter, the permafrost zones show diagnostic long term freezing indices and thawing indices. The warmer boundary of the zone of continuous permafrost traverses the mean annual air temperature (MAAT). The boundary between discontinuous and sporadic permafrost lies just on the cold side of 0° C MAAT. The sporadic permafrost zone includes the zone of ice caves and the regions with patches of ice beneath ponds and peatbogs, extending to 5° C MAAT at a thawing index of 4000 degree days per year. The relationship is applicable to Norway, Iceland, Spitzbergen, Canada and the People's Republic of Mongolia. There are some marked variations in lapse rate from one environment to another, the most marked of which occurs above tree line where the lapse rate increases markedly in winter, though not in summer. This produces a change in MAAT of 2.5° C on Plateau Mountain. The changes also occur at some points in non-permafrost areas and it appears likely that they are due to spatial and seasonal changes in albedo. Whatever the cause, the variations in lapse rate indicate that calculations of past world climate change based on data from one area may be misleading.

Natural Convection Above Fires—An Analytical Solution

In this paper an analytical solution of the problem of turbulent buoyant plume, in a dry and calm atmosphere with an arbitrary lapse rate variation, is attempted. The results are compared with those given in an earlier publication based on the solution obtained by a Pace analog computer.

Radiative transfer effects in natural convection above fires—general case

In this paper the effect of radiation, on the overall dynamics of a hot plume above large fires, has been considered. An attempt has been made to give a unified approach to the problem of radiative heat transfer as applied to the phenomena of natural convection. This is obtained by deriving an approximate multi-dimensional transfer equation for heat radiation from the Schwarzschild’s equation. The plume material is assumed to be grey and is characterized by a general absorption coefficient. The outside atmosphere is considered calm and is, otherwise, in a state of arbitrary lapse rate variation. The results, given here, are of a more general nature. The solution curves, for some representative values of the parameters, are obtained and are compared with the corresponding ones given in our earlier publications. Also, from the general transfer equation, the asymptotic cases, corresponding to large and small absorption coefficients, are derived.

Natural convection above fires

The turbulent natural convection above fires in a dry calm atmosphere with a constant lapse rate has been the subject of several recent investigation (see references). The present paper presents solution curves from which the natural convection may be computed over a fire of arbitrary size in an atmosphere with arbitrary lapse-rate variation. The independent parameters of fire size, energy release rate (buoyancy), momentum release rate and atmospheric lapse rate are given over the expected range of values. The arbitrary variation of lapse rate is thus calculable as piecewise constant.