Diurnal Temperature Amplitude Research Articles

Skin Temperature Analysis and Bias Correction in a Coupled Land-Atmosphere Data Assimilation System

In an initial investigation, remotely sensed surface temperature is assimilated into a coupled atmosphere/land global data assimilation system, with explicit accounting for biases in the model state. In this scheme, an incremental bias correction term is introduced in the model's surface energy budget. In its simplest form, the algorithm estimates and corrects a constant time mean bias for each gridpoint; additional benefits are attained with a refined version of the algorithm which allows for a correction of the mean diurnal cycle. The method is validated against the assimilated observations, as well as independent near-surface air temperature observations. In many regions, not accounting for the diurnal cycle of bias caused degradation of the diurnal amplitude of background model air temperature. Energy fluxes collected through the Coordinated Enhanced Observing Period (CEOP) are used to more closely inspect the surface energy budget. In general, sensible heat flux is improved with the surface temperature assimilation, and two stations show a reduction of bias by as much as 30 Wm(sup -2) Rondonia station in Amazonia, the Bowen ratio changes direction in an improvement related to the temperature assimilation. However, at many stations the monthly latent heat flux bias is slightly increased. These results show the impact of univariate assimilation of surface temperature observations on the surface energy budget, and suggest the need for multivariate land data assimilation. The results also show the need for independent validation data, especially flux stations in varied climate regimes.

Evaluation of six parameterization approaches for the ground heat flux

There are numerous approaches to the parameterization of the ground heat flux that use different input data, are valid for different times of the day, and deliver results of different quality. Six of these approaches are tested in this study: three approaches calculating the ground heat flux from net radiation, one approach using the turbulent sensible heat flux, one simplified in situ measurement approach, and the force-restore method. On the basis of a data set recorded during the LITFASS-2003 experiment, the strengths and weaknesses of the approaches are assessed. The quality of the best approaches (simplified measurement and force-restore) approximates that of the measured data set. An approach calculating the ground heat flux from net radiation and the diurnal amplitude of the soil surface temperature also delivers satisfactory daytime results. The remaining approaches all have such serious drawbacks that they should only be applied with care. Altogether, this study demonstrates that ground heat flux parameterization has the potential to produce results matching measured ones very well, if all conditions and restrictions of the respective approaches are taken into account.

Xylem temperatures during winter in conifers at the alpine timberline

Trees at the alpine timberline are exposed to extreme temperatures during winter. These temperature conditions affect the hydraulic properties of the xylem because frozen sections block water flux and freeze–thaw events can induce embolism. In this study, winter temperature regimes in the xylem of Picea abies and Pinus cembra growing at the Central Alps timberline were analysed. During mid winter nights minimum xylem temperatures were down to −20.5 °C. In late winter, daytime xylem temperatures up to 22.8 K above air temperature and extreme diurnal temperature amplitudes of up to 30 K were observed. The number of freeze–thaw events was highest (115 events from September to May) in sun exposed parts at the top of the trees, and decreased towards the trunk base as well as from the trunks surface to its centre and from distal to proximal twig sections. Freezing and thawing rates were higher at the top of the tree (up to 5.4 and 7.0 K h −1) than at the trunk base (up to 4.4 and 4.5 K h −1). Our study demonstrates that sun exposed parts of timberline trees exhibit most extreme temperature minima and maxima, highest rates of temperature change, as well as the highest number of freeze–thaw events. These conditions are favourable to induce embolism. In contrast, the xylem of less exposed crown parts was found to be frozen and consequently separated from trunk water resources during prolonged periods. The observed complexity of temperature regimes may be relevant for tree life at high altitudes as temperature has been suggested to be a limiting factor at the timberline.

Relationship between passive microwave‐derived snowmelt and surface‐measured discharge, Wheaton River, Yukon Territory, Canada

AbstractSnow volume and melt timing are major factors influencing the water cycle at northern high altitudes and latitudes, yet both are hard to quantify or monitor in remote mountainous regions. Twice‐daily special sensor microwave imager (SSM/I) passive microwave observations of seasonal snow melt onset in the Wheaton River basin, Yukon Territory, Canada (∼60 ° 08′05″N, ∼134 ° 53′45″W), are used to test the idea that melt onset date and duration of snowpack melt–refreeze fluctuations control the timing of the early hydrograph peaks with predictable lags. This work uses the SSM/I satellite data from 1988 to 2002 to evaluate the chronology of melt and runoff patterns in the upper Yukon River basin. The Wheaton River is a small (875 km2) tributary to the Yukon, and is a subarctic, partly glacierized heterogeneous basin with near‐continuous hydrographic records dating back to 1966. SSM/I pixels are sensitive to melt onset due to the strong increase in snow emissivity, and have a robust signal, in spite of coarse (>25 × 25 km2) pixel resolution and varied terrain. Results show that Wheaton River peak flows closely follow the end of large daily variations in brightness temperature of pixels covering the Wheaton River, but the magnitude of flow is highly variable, as might be expected from interannual snow mass variability. Spring rise in the hydrograph follows the end of high diurnal brightness temperature (Tb) amplitude variations (DAV) by 0 to 5 days approximately 90% of the time for this basin. Subsequent work will compare these findings for a larger (7250 km2), unglacierized tributary, the Ross River, which is farther northeast (∼61 ° 59″40″N, ∼132 ° 22″40″W) in the Yukon Territory. These techniques will also be used to try to determine the improvement in melt detection and runoff prediction from the higher resolution (∼15 × 15 km2) advanced microwave scanning radiometer for EOS (AMSR‐E) sensor. Copyright © 2006 John Wiley & Sons, Ltd.

Beneficial effects of regular exercise on sleep in old F344 rats

With aging there is a significant decline in the normal architecture of sleep and a reduction in the diurnal amplitude of core body temperature. Regular moderate exercise has been shown to have a positive impact in the elderly and here we investigate whether sleep–wake patterning can also be improved. Young (3 months) and old (22 months) F344 rats were exercised once a day for 50 min at night onset over an 8-week period. Thereafter, polysomnographic recordings were obtained immediately after exercise. To determine the lasting consequences of exercise, sleep was also recorded 2 days and 2 weeks after exercise had ended. Old rats that were exercised had a significant weight loss, were awake more during the last third of their active period, had less sleep fragmentation and the amplitude of the diurnal rhythm of core body temperature was significantly increased. Old exercised rats also had an overall increase in the amplitude of EEG power (0.5–16 Hz) during wake and theta EEG power during REM sleep. In young rats regular exercise increased EEG delta power (0.5–4 Hz) during NREM sleep. Our data indicate regular exercise in old rats improves sleep architecture, EEG power and diurnal rhythm of temperature.

A diagnostic model of the diurnal cycle of sea surface temperature for use in coupled ocean‐atmosphere models

On the basis of a method of estimating the diurnal amplitude of sea surface temperature (SST) as a function of the diurnal integrals of surface heat and momentum fluxes, a parameterization scheme of the diurnal cycle of SST is implemented in a one‐dimensional ocean mixed‐layer model. Many coupled ocean‐atmosphere models using bulk mixed‐layer schemes underestimate the diurnal cycle in sea surface temperature by up to 2°C. This discrepancy is caused by coarse vertical resolution in the upper grid boxes of the ocean components. A simple solution is suggested by adding one extra transient level: a variable‐depth diurnal sublayer within the top model level which accommodates the diurnal buoyancy cycle. A one‐dimensional mixed‐layer model with 10‐m resolution and with sublayer simulates diurnal SSTs close to those observed from the Tropical Ocean Global Atmosphere/Coupled Ocean Atmosphere Response Experiment (TOGA/COARE) with typical errors of about 0.1°C. The impact of improved SSTs on surface heat fluxes is also shown by coupling the one‐dimensional mixed‐layer model with sublayer to an atmospheric boundary layer model.

Spatial and temporal variations of model‐derived diurnal amplitude of sea surface temperature in the western Pacific Ocean

The diurnal amplitude of sea surface temperature (SST) at 1‐m depth is estimated with a simple empirical model in the region of 80°E–160°W, 60°S–60°N covering the western Pacific Ocean using 4 years of satellite‐derived wind speed, solar radiation, and latent heat flux data. The advantage of this indirect method is that the diurnal amplitude of SST (ΔSST) can be obtained even in cloudy areas. ΔSST is large in the tropics through the year. Summer ΔSST in the middle and high latitudes of the Northern Hemisphere, especially around Japan, is larger than that of the Southern Hemisphere. However, ΔSST in the Kuroshio and its extension regions is smaller compared with that in its surrounding ones because of higher wind speed. In the Bay of Bengal, the South China Sea, and the Timor Sea, ΔSST becomes largest in spring, when the surface wind becomes weak in the transition of the monsoon. The period of about 35–50 days is clearly seen in the temporal variation of ΔSST in the tropics. This reflects the Madden‐Julian oscillation. Furthermore, there are some differences in ΔSST between El Niño and La Niña periods. The authors then investigate how clouds affect the detection of ΔSST. If sampling is limited to clear areas only, the areas of strong solar radiation and weak wind are selectively picked up, and the probability that larger ΔSST is sampled increases. The mean of the ΔSST sampled from clear areas only is greater by 0.2–0.3 K compared with the actual mean.

Sensitivity of satellite microwave and infrared observations to soil moisture at a global scale: Relationship of satellite observations to in situ soil moisture measurements

This study presents a systematic and integrated analysis of the sensitivity of the available satellite observations to in situ soil moisture measurements. Although none of these satellites is optimized for land surface characterization, before the launches of the SMOS‐ and HYDROS‐dedicated missions they are the only potential sources of global soil moisture measurements. The satellite observations include passive microwave emissivities, active microwave scatterometer data, and infrared estimates of the diurnal amplitude of the surface skin temperature. The Global Soil Moisture Data Bank provides in situ soil moisture measurements in five separate regions. This simultaneous analysis of various satellite observations and the large amount of in situ measurements has two major advantages. First, this analysis helps identify and separate the physical mechanisms that affect the satellite observations. For example, we show that the passive microwave polarization differences at 19 GHz and above are essentially sensitive to the vegetation and not to the soil moisture (i.e., the correlation between microwave observations and soil moisture is only indirect and comes from the statistical correlation between vegetation and soil moisture). Second, this analysis enables an objective comparison of the relative potential of the various satellite observations for soil moisture retrieval when other conditions are held constant. The second part of this study benefits from this synthesis to derive a relationship between satellite observations and soil moisture at a global scale.

Response of effective quantum yield of photosystem 2 to in situ temperature in three alpine plants

The response of effective quantum yield of photosystem 2 (ΔF/Fm’) to temperature was investigated under field conditions (1 950 m a.s.l.) in three alpine plant species with contrasting leaf temperature climates. The in situ temperature response did not follow an optimum curve but under saturating irradiances [PPFD >800 µimol(photon) m−2s−1] highest ΔF/Fm’ occurred at leaf temperatures below 10°C. This was comparable to the temperature response of antarctic vascular plants. Leaf temperatures between 0 and 15°C were the most frequently (41 to 56%) experienced by the investigated species. At these temperatures, ΔF/Fm’ was highest in all species (data from all irradiation classes included) but the species differed in the temperature at which ΔF/Fm’ dropped below 50% (Soldanella pusilla >20°C, Loiseleuria procumbens >25°C, and Saxifraga paniculata >40°C). The in situ response of ΔF/Fm’ showed significantly higher ΔF/Fm’ values at saturating PPFD for the species growing in full sunlight (S. paniculata and L. procumbens) than for S. pusilla growing under more moderate PPFD. The effect of increasing PPFD on ΔF/Fm’, for a given leaf temperature, was most pronounced in S. pusilla. Despite the broad diurnal leaf temperature amplitude of alpine environments, only in S. paniculata did saturating PPFD occur over a broad range of leaf temperatures (43 K). In the other two species it was half of that (around 20 K). This indicates that the setting of environmental scenarios (leaf temperature×PPFD) in laboratory experiments often likely exceeds the actual environmental demand in the field.

Initial full-diurnal-cycle mesopause region lidar observations: diurnal-means and tidal perturbations of temperature and winds over Fort Collins, CO (41°N,105°W)

The Colorado State Sodium lidar has been upgraded to a two-beam system capable of simultaneous measurements of mesopause region temperature and winds, over full diurnal-cycles, weather permitting. Though our lidar is a modest system with a power-aperture product of only 0.06 W m 2 , good data quality is demonstrated by means of contour plots depicting a 80-h continuous observation between August 9th and 12th, showing the existence of atmospheric waves with different periods along with their coherence and interactions. The salient feature of data with full-diurnal-cycle coverage lies in its ability to describe the vertical profiles of dynamical fields (temperature, zonal and meridional winds) as a unique linear superposition of diurnal-mean and oscillations with different tidal periods, plus a residual term. In this manner, we investigate diurnal-means and oscillations with diurnal and semidiurnal periods. Using 6 data sets between July 17 and August 12, each covering a full-diurnal-cycle as a case study, we found considerable day-to-day variability, as much as 20 K , 35 and 75 m/s for diurnal-mean temperature, zonal wind and meridional wind, respectively, and as 15 K , and 50 m/s , for the diurnal and semidiurnal tidal temperature and wind amplitudes, respectively. While a minimum of 3 full diurnal cycles appears to be adequate in the case studied here, the 6-day composite yields diurnal-means and diurnal tides in agreement with model predictions very well. Since the resulting amplitudes and phases of the observed diurnal oscillations agree well with the global scale wave model, GSWM00 predictions, we conclude that the migrating diurnal tide contributes significantly to the observed oscillations with diurnal period over Fort Collins, CO (41°N, 105°W). Unlike the diurnal perturbations, the observed semidiurnal amplitudes and phases differ from the GSWM00 predictions with considerably smaller model amplitudes. The coherence of solar forcing is found to prevail over the variability for diurnal-mean as well as both tidal oscillations, leading to expected convergence to climatology in a multi-day composite observation. The possible causes for the observed variability, and the role of planetary waves and nonlinear interactions are discussed, along with future studies to assess the extent of local perturbations that may exist in the observed data.

The atmospheric boundary layer in the CSIRO global climate model: simulations versus observations

A 5-year simulation of the atmospheric boundary layer in the CSIRO global climate model (GCM) is compared with detailed boundary-layer observations at six locations, two over the ocean and four over land. Field observations, in the form of surface fluxes and vertical profiles of wind, temperature and humidity, are generally available for each hour over periods of one month or more in a single year. GCM simulations are for specific months corresponding to the field observations, for each of five years. At three of the four land sites (two in Australia, one in south-eastern France), modelled rainfall was close to the observed climatological values, but was significantly in deficit at the fourth (Kansas, USA). Observed rainfall during the field expeditions was close to climatology at all four sites. At the Kansas site, modelled screen temperatures (Tsc), diurnal temperature amplitude and sensible heat flux (H) were significantly higher than observed, with modelled evaporation (E) much lower. At the other three land sites, there is excellent correspondence between the diurnal amplitude and phase and absolute values of each variable (Tsc, H, E). Mean monthly vertical profiles for specific times of the day show strong similarities: over land and ocean in vertical shape and absolute values of variables, and in the mixed-layer and nocturnal-inversion depths (over land) and the height of the elevated inversion or height of the cloud layer (over the sea). Of special interest is the presence climatologically of early morning humidity inversions related to dewfall and of nocturnal low-level jets; such features are found in the GCM simulations. The observed day-to-day variability in vertical structure is captured well in the model for most sites, including, over a whole month, the temperature range at all levels in the boundary layer, and the mix of shallow and deep mixed layers. Weaknesses or unrealistic structure include the following, (a) unrealistic model mixed-layer temperature profiles over land in clear skies, related to use of a simple local first-order turbulence closure, (b) a tendency to overpredict cloud liquid water near the surface.

Impacts of Diurnal Cycle of SST on the Intraseasonal Variation of Surface Heat Flux over the Western Pacific Warm Pool

Based on the method of estimating the diurnal amplitude of sea surface temperature (SST) as a function of daily averaged wind speed, precipitation and peak surface radiation, a parameterization scheme of diurnal cycle of SST is developed in the present study, Integrations to National Center for Atmospheric Research (NCAR) Community Climate Model (CCM3), separately forced by observed weekly SSTs with and without diurnal cycle of SST, are compared. Surface observation obtained from the Improved Meteorology (IMET) buoy during TOGA COARE Intensive Observation Period is applied to verify the SST parameterization, as well as a validation to the results from the CCM3 simulation. It is shown that the superposition of diurnal cycle of SST to the forced weekly SST makes a more realistic representation of the surface structure of intraseasonal oscillation over the western Pacific warm pool.

Migrating thermospheric tides

The capabilities of the global‐scale wave model (GSWM) [Hagan et al., 1995, 1999] are extended to include migrating thermospheric solar tides. The GSWM thermospheric tidal forcing parameterization is based on neutral gas heating calculated from first principles in the National Center for Atmospheric Research (NCAR) thermosphere/ionosphere electrodynamics general circulation model (TIE‐GCM). This is the first time that a physics‐based thermospheric forcing scheme has been used in a model like GSWM. Previous two‐dimensional steady state linear tidal models used exospheric temperature measurements to calibrate upper atmospheric tidal forcing. New GSWM results illustrate thermospheric tidal responses that are largely consistent with tides in the TIE‐GCM. Diurnal temperature amplitudes increase with increasing solar activity, but there is no analogous diurnal wind response. The thermospheric semidiurnal tide is much weaker than the diurnal tide. Semidiurnal temperature perturbations peak in the lower thermosphere where the semidiurnal forcing maximizes. The new in situ results must be combined with the GSWM upward propagating tide in the lower thermosphere, because the upward propagating components dominate the semidiurnal response throughout the region and the diurnal response below ∼130 km. In situ forcing accounts for most of the diurnal response aloft. Our preliminary evaluation of the GSWM thermospheric predictions is inconclusive. More extensive evaluations are necessary to make a firm assessment of whether the model captures the salient features of the seasonal and solar cycle variability of thermospheric tides.

Effect of tidal variability on the mean diurnal variation of noctilucent clouds

Lidar observations of noctilucent clouds (NLCs) have shown that the mean diurnal variations of the NLC altitude and backscatter ratio are dominated by semidiurnal components that are at odds with previous model simulations using mean tidal temperature variations. Measured tides, however, exhibit a strong day‐to‐day variability so that, as a consequence of the highly nonlinear response of NLC models to temperature changes, the mean diurnal NLC variation cannot be obtained from the mean diurnal temperature variation but has to be simulated by averaging over NLC samples computed from individual diurnal temperature variations. Therefore a simple model of tidal variability based on means and standard deviations of the diurnal and semidiurnal temperature amplitudes and phases is set up so that samples of the diurnal temperature variation and corresponding NLC samples can be computed. The resulting mean diurnal variations of the NLC altitude and backscatter ratio show a good overall agreement with the observed variations and clearly reflect the strong semidiurnal components. Discrepancies between observed and simulated results can be attributed at least partly to deficiencies of the tidal variability model which, in particular, does not take into account any coherence between tidal and planetary wave‐associated temperature variations.

Temperature and heterogeneity of emergence time in oilseed rape

SUMMARYEmergence of oilseed rape cultivars with known differences in germination profile was examined by controlled sowings in the field at mean temperatures between 2 and 10°C. Early percentiles, up to the 50th in two cultivars (Rocket and Martina) and up to the 20th in a third (Comet), responded to temperature similarly at all sowings, in that 1/time to emergence of a percentile (emergence rate) increased exponentially with temperature above an intercept of‐1°C. For these percentiles, emergence occurred at a similar thermally weighted time over the whole range of temperature, indicating the peak of the first flush of seedlings is predictable. Percentiles higher than those cited above displayed increasing non‐germination (probably secondary dormancy) as temperature declined towards winter. The maximum non‐germination ranged between 50% and 80% among the cultivars. In sowings during and just after winter, the emergence rate of these higher percentiles was lower than at a comparable temperature before winter. A portion of non‐germinating seeds of the two most heterogeneous cultivars overwintered and emerged synchronously in April from a range of pre‐ and post‐winter sowings, probably stimulated by increasing diurnal temperature amplitude from 7 to 15K. At low temperature, therefore, cultivars exhibited great heterogeneity in the emergence profile, those with more heterogeneity being more likely to give rise to temporally separate weed or feral populations. The findings are discussed in the context of weediness and transgene movement in the oilseed rape metapopulation.

Analysis of Energy Balance Components as a Function of Orography and Land Use and Comparison of Results with the Distribution of Variables Influencing Local Climate

During 1992 and 1995 in the Upper Rhine valley between Karlsruhe in the north and Basel in the south 36 energy balance stations were installed to analyze the spatial and temporal behavior of the components of the energy balance. A second aim of the project ‘Regio-Klima-Projekt’ (REKLIP) was to study the dependence of climatic variables on the energy balance. Three main influences on spatial variation in energy balance components were detected: orography, precipitation and land use. Concerning the dependence of the climatic variables on the energy balance it can be stated that the mean diurnal amplitude of temperature shows a good correlation with the mean diurnal sensible heat flux, while the diurnal amplitude of the specific humidity correlates with the mean diurnal latent heat flux. Both these results are in good agreement with theoretical considerations. Consequently, areas with enhanced sensible heat flux values show higher monthly mean temperature maxima and also a greater numbers of summer days, while areas with higher latent heat flux values indicate enhanced monthly mean humidity maxima.

A multiyear hourly sea surface skin temperature data set derived from the TOGA TAO bulk temperature and wind speed over the tropical Pacific

A theoretical relationship is derived to estimate the sea surface skin temperature from near‐surface wind speed and the diurnal variation of sea surface bulk (or bucket) temperature. Coefficients in the relation are determined using the R/V Franklin data during the Tropical Ocean‐Global Atmosphere (TOGA) Coupled Ocean‐Atmosphere Response Experiment (COARE). In contrast to previous methods, surface energy flux data are not explicitly required but rather are implied by the temporal variation of bulk temperature. A multiyear hourly skin temperature data set is obtained using data of bulk temperature at 1‐m depth and wind speed from the TOGA Tropical Atmosphere‐Ocean (TAO) moored buoys spanning the tropical Pacific Ocean from 95°W in the eastern Pacific to 137°E in the western Pacific between 9°N and 8°S. The diurnal amplitude of skin temperature reaches its maximum of about 2.8 K for daily averaged wind speed between 1–2 m s−1 and skin temperature between 20°–21°C and decreases with greater wind speeds. The most frequent amplitude is about 0.5 K, the average amplitude is 0.65 K, and the accumulated frequency for amplitudes greater than 1 K is 10% within the parameter space of daily averaged wind speed between 1 and 15 m s−1 and daily averaged skin temperature between 18° and 34°C.

The effect of temperature on sensory quality, chemical composition and growth of carrots (Daucus carota L.). III. Different diurnal temperature amplitudes

SummaryData from experiments with carrots grown in phytotrons under different day and night temperatures at two locations in Norway and three harvesting dates were treated by means of Principal Component Analysis (PCA). No effect of the single temperature amplitudes were found, the significant main effects were due to the mean temperature levels of 12 and 188C, location and harvest date. The PCA visualized the effect of mean temperature level on sensory, chemical and physical variables. Differences between the two groups were mainly caused by variation in sensory variables, the first group being characterized by high score for whiteness, sweetness, acidic taste, crispness, juiciness, glucose, fructose and root length. The other group had a high score for colour, odour, overall taste and flavour parameters, firmness, dry matter, sucrose, a and b-carotene, root weight and root diameters.

Land Surface–Induced Regional Climate Change in Southern Israel

Since the mid-1960s, the southern part of Israel has experienced major land use changes following the start of the irrigation scheme and the subsequent intensification of agricultural practice. Several studies, mainly based on the analysis of climatic time series, have shown that this has been followed by a significant change of the local climate, especially during the summer and early fall. They indicate a reduced diurnal amplitude of surface air temperature and wind speed, and a threefold increase of the October (early wet season) convective precipitation. In this paper, these phenomena are investigated by simulating the influence of the land surface on local meteorological variables with a two-dimensional version of a mesoscale atmospheric model containing a detailed land surface scheme. Particular attention is given to the correct estimation of land surface parameters from soil and vegetation maps and remote sensing data. The simulations confirm the observed reduction of the diurnal amplitude of temperature and wind speed when replacing a semiarid surface by a partly irrigated one. Furthermore, it is shown that the potential for moist convection increases with the surface moisture availability and is rather insensitive to the surface roughness.

Selective absorption of solar radiation and upper ocean temperature in the equatorial western Pacific

The solar radiation absorbed by seawater in the upper 0.45 m within the Tropical Ocean‐Global Atmosphere (TOGA) Coupled Ocean‐Atmosphere Response Experiment (COARE) domain is estimated from the observed surface heat fluxes and subsurface temperature during the TOGA COARE Intensive Observation Period. On the average, more than 39% of the net surface solar irradiance is estimated to be absorbed within the first 0.45 m. This value is higher than previous estimates. The observed absorption is applied to modify the parameterized transmittance profile representing the COARE domain, which is bordered by the optical water types IA, IB, and II [Jerlov, 1968]. The original and modified profiles of solar irradiance are prescribed in a one‐dimensional ocean model to test their effects on the model responses to the observed surface fluxes. The modified profiles for the three types of water all produce better simulation results than the corresponding original profiles in terms of the diurnal and intraseasonal sea surface temperature amplitudes. The model results support our estimate that the near‐surface absorption of solar radiation in the COARE region is stronger than that suggested by the water types IA, IB, and II.