1. Introduction
The height of the atmospheric boundary layer Zi governs the vertical mixing of atmospheric pollutant and has been used as an important parameter in air pollution monitoring and boundary layer studies. It is also an important scaling length for the normalization of boundary layer parameters such as fluxes and variance including vertical gradients of wind, potential temperature, and moisture. This characteristic level is required as a basic input parameter in numerical weather and climate forecasting models of the boundary layers (Stull 1988; Beyrich and Weill 1993).
The daytime continental convective boundary layer (CBL) considered in the present study is generally capped by a temperature inversion layer that arises in the morning in response to solar heating and the subsequent vertical mixing. It defines the interface between a well-mixed layer and the free atmosphere and prevents the vertical exchange of pollutants toward the free atmosphere. This interfacial layer called the entrainment zone is characterized by a significant vertical gradient of virtual potential temperature and a minimum heat flux. According to Stull (1988), the CBL height is the top of mixed layer, often defined as the average base of the overlying stable layer, and responds to surface forcings with a timescale of about an hour or less. Different definitions of CBL height have been proposed based on various physical quantities. Sullivan et al. (1998) defines Zi as the height where the vertical gradient of potential temperature has its maximum value. This level corresponds to the middle of the inversion layer. It has also been defined as the height where the buoyancy flux reaches its most negative value (Deardorff et al. 1980; Wyngaard and LeMone 1980). In that case, the CBL height is defined as the base of the temperature inversion. During daytime, low and shallow stratus clouds can exist in or at the CBL top and often occupy a significant portion of the CBL. However, there is no consensus as to how to define CBL height in the presence of clouds. In that case, two characteristic levels are identified. The first one is the cloud base corresonding to the height of dry mixing layer and the second one is the cloud top generally linked with the inversion layer. The difficulty in determining cloudy boundary layer height is due to the fact that a new turbulent source appears in the cloud layer linked with radiative and condensation/evaporation processes. This turbulent source can be strong at the cloud top and on the cloud edge when the cloud layer is fragmented. We will consider the case in which the cloud top corresponds to the Zi level.
The entrainment in the interfacial layer can create a strong vertical gradient in the temperature and humidity profiles, which causes a maximum in the profile of the refractive index parameter
Recently, different
Actually, although UHF radar is a more recent tool used in the boundary layer studies and monitoring, remote sensing of the boundary layer and in particular the determination of Zi have a long history. The work reported by Kaimal et al. (1982) is a representative example showing CBL depth estimation with a K-band, X-band, and S-band radar, a lidar, and a sodar during the PHOENIX experiment. The remotely determined Zi level, based on reflectivity profiles, agreed with the CBL depth deduced from different in situ sensors within about ±10%. In an earlier study, Campistron (1975) showed the capability of a millimetric radar for the detection of the CBL top and other stable layers located in the free atmosphere.
In the present paper, the behavior of
2. Overview of the TRAC experiment: Data collection and processing
a. TRAC experiment
The data used in the present study were collected during the Turbulence, Radar, Aircraft, Cells (TRAC) experiment, the description of which is detailed by Campistron et al. (1999). The experiment was designed to investigate coherent structures in the boudary layer, and to quantify turbulent and coherent transport, surface heat flux and entrainment, and interactions between the boundary layer and clouds. An important goal of the experiment was to provide a relevant database for numerical simulation of the boundary layer. It was carried out from 15 June to 5 July 1998 over a rural flat area of about 60 km × 60 km located in the middle part of France, several hundred kilometes away from the influence of high mountain ranges and maritime zones. Important instrumental facilities were deployed to reach the scientific objectives. Among them, a C-band Doppler radar, two UHF wind profilers, two powerful sodars, two instrumented aircrafts, and five surface meteorological stations equipped to measure turbulent heat fluxes and other more conventional atmospheric parameters including radiative fluxes were used. Rawinsondes were launched five times a day (0200, 0500, 0800, 1100, and 1400 LST) from the main site of the experiment (48.21°N, 1.68°E) with a typical vertical resolution of about 30 m.
b. UHF profiler
The UHF wind profiler used is the DEGREWIND PCL1300 profiler, designed and manufactured by the Etablissement Degreane. Located at the rawinsonding site, it was operated continuously during the entire campaign in order to observe mean and turbulent clear air conditions in the lower atmospheric layer. The main characteristics of this Doppler radar were a 1238-MHz transmitted frequency, with a 4-kW peak pulse power, a 25-kHz pulse repetition frequency, and a 150-m pulse length. In order to get the three components of the wind, the profiler alternatively used five beam positions—one vertical and four oblique—with a one-way half-power aperture of 8.5°. The oblique beams, with an off-zenith angle of 17°, were disposed every 90° in azimuth. Signals of time series were acquired with range gates evenly spaced along the radial at 75-m intervals, starting at 65 m AGL. A running coherent integration over 125 points on the times series was performed. In addition, 20 successive Doppler spectra, which were obtained from a 128-point discrete Fourier transform applied on the decimated series (1 point out of 125 points was used), weighted with an Hanning window, were incoherently averaged. As a result, the dwell time on each beam was 13 s, the spectral resolution 0.1 m s−1, and the Nyquist velocity ±6.1 m s−1.
The spectra, usually contaminated by noise and nonmeteorological echoes, were carefully edited in order to extract the first three moments of the atmospheric backscattered peak. In the first step, the mean noise level was determined using the objective technique proposed by Hildebrand and Sekhon (1974). The zero velocity and the two adjacent spectral lines, usually contaminated by ground clutter, were discarded and replaced by interpolated values. In addition, the statistical averaging technique developed by Merritt (1995) was applied to remove strong coherent-like echoes (bird, aircraft, etc.). Usually, distinct Doppler peaks emerge above the noise level. Thus, in the second step of data processing, the selection of the meteorological peak is done through a consensus based on vertical, temporal, and spectral continuity as well as thresholding. In fact, the consensus gives a Gaussian weight to each spectral line remaining after thresholding, the value of which depends on the continuity tests. The first three moments are computed with the weighted contiguous spectral lines selected during the last 30 min. Tests have shown that this consensus technique, when removing or smoothing out spurious echoes, performs a temporal average over the considered period of the three moments of the meteorological peak. The use of a consensus period of 5 min or less results in more fluctuating values and sometimes fails to remove unwanted spectral lines. However, when averaging in time, these high-temporal definition moments, the values obtained with the 30-min consensus are recovered. This in particular shows that the spectral width discussed in this paper is not subject to a perceptible broadening factor due to the use of a long-duration-based consensus. Since all the raw Doppler spectra are recorded, it is then possible during offline processing to optimize the parameterization of the consensus to obtain the best results. For the data presented here, we used only a five-beam cycle acquired every 5 min. Additionally, we used only the reflectivity provided by the vertical beam. Tests have shown that reflectivity values acquired on the vertical or oblique beam are in fairly good agreement (with a difference less than 2 dB).
Quality control of the UHF profiler data was made during a 1-yr validation campaign with the use of rawinsondings, sodar, and sonic anemometers (Dessens et al. 1997). On the other hand, the ability of UHF radar to detect rain of even weak intensity was used, in comparison with disdrometer measurements at the ground, to calibrate the instrument in reflectivity and to assess vertical velocity and spectral width retrieval (Campistron et al. 1997).
c. C2n
The CBL top is usually characterized by a strong increase in the potential temperature as well as a strong decrease in the mixing ratio. Thus, these two factors that add positively in (2) enhance the radar signal provided, according to (1), that sufficient turbulent mixing exists to create refractivity index irregularities at half the radar wavelength. This is the principal scale of the inertial subrange participating in the radar signal (Tatarskii 1961).
In a well-mixed CBL, the vertical profiles of potential temperature and mixing ratio are, on average, nearly constant with height (Stull 1988). Despite the strong turbulence, we might expect weak radar echoes from refractive index irregularities in the CBL. Grimsdell and Angevine (1998) have suggested that, in clear-air mixed layers, part of the radar return might be contaminated by hard targets such as insects.
d. Doppler spectra width
3. Comparison between CBL height estimated from rawinsonde data and UHF C2n
In this section a comparison is made for two characteristic days of TRAC between the vertical profiles of
a. Definition of the CBL top
As discussed previously in this paper, we consider the CBL top as the height corresponding to the thermal inversion layer (maximum thermal gradient). This definition is totally compatible with both dry and cloudy CBLs where the cloud layer is related to the surface layer, as generally observed in continental conditions. In that case, the CBL height Zi was determined from rawinsonde data using the gradient method of Sullivan et al. (1998).
b. Analysis of two case studies
For this study, we selected a clear-air CBL (19 June 1998) and a cloud-topped CBL (29 June 1998). They are representative of the main difficulties encountered in Zi determination using radar. For these two days, the vertical profiles of θυ, q, virtual potential temperature gradient (dθυ/dz), and M2 deduced from rawinsonde observations in the early morning, near midday, and in the midafternoon (only for the cloudy day), are presented in Figs. 1 and 2, respectively. The vertical derivatives were computed using a centered difference at each radiosonde level. A running average over 150 m was applied on the M2 profiles in order to reduce computing noise. Associated with these thermodynamical parameters,
1) Case of 19 June 1998
On 19 June 1998, the observations were made under fair weather conditions, with a weak synoptic wind of less than 7 m s−1 and a nearly cloud free CBL. Figure 1a displays the vertical profiles obtained at about 0800 LST. The profiles of θυ and its vertical derivative ∂θυ/∂z show two distinct strong stable layers located between 0.3 and 0.7 km and between 1.1 and 1.6 km. These layers are also marked by strong vertical variations of q and correspond to two major peaks in the M2 profile, a result expected from Eq. (2) considering the vertical evolution of θυ and q.
The vertical profile of
Considering that these observations were made in the early morning and taking into account the temporal continuity of the UHF observations and rawinsonding measurements, we found that the most probable CBL top is associated with the lower stable layer. Based on the gradient method, the height of the Zi level was located at 0.5 km, that is, 100 m above the corresponding
At about 1100 LST on the same day, the vertical profiles presented in Fig. 1b show that the estimations of the CBL height are simpler than in the early morning. We are left with a
2) Case of 29 June 1998
On 29 June 1998, a humid but weak (less than 6 m s−1) westerly flow prevailed in the CBL. Figures 2a to 2c present vertical profiles obtained from radiosondes and UHF radar at about 0802, 1119, and 1403 LST, respectively. This fair weather day differs from the first case study because of the partly cloudy sky present from early morning to late afternoon with cloud fraction varying from 60% to 80%, according to visual reports made at the UHF site. Radiosonding offers only a snapshot in time and space of the atmosphere. Thus, in order to get a more complete description of the cloud layer, we used measurements collected by one of the two research aircraft that performed continuous flights over the study area between 0916 and 1207 LST.
This flight was divided into eight 45-km constant levels and course legs between 100 and 1800 m above ground and centered on the vertical of the UHF. Four legs were performed in a north–south-oriented vertical plane and the other in an east–west-oriented vertical plane. Following Grimsdell and Angevine (1998), the cloud-base height was taken to be the lifting condensation level deduced from the aircraft data series of pressure, temperature, and mixing ratio sampled along the flight every 4 m. The results for the considered flight period show a mean cloud-base height of 800 m and an increase in the cloud base of about 150 m toward both the north–south and the west–east directions over the 45-km legs. In addition, on average, there was a temporal increase of about 120 m during the 3-h flight. At the beginning of the flight, during the ascent, the aircraft crossed the cumulus layer and visual report indicated a cloud-base and cloud-top height of 900 and 1400 m, respectively. The same observations made at the end of the flight situated the cloud-base and cloud-top level at about 950 and 1400 m, respectively.
The early morning vertical profiles at 0802 LST in Fig. 2a display similar characteristics to those of the previously discussed day (Fig. 1a). With the same reasoning, we identify a residual layer including clouds, between about 1.0 and 1.3 km, with a nearly constant virtual potential temperature with height, capped by a stable layer extending, from 1.3 to 1.45 km. In this inversion layer, the vertical increase of the potential temperature and the vertical decrease of the mixing ratio are much more acute than in the case of the cloud-free day. The most probable CBL top in Fig. 2a is found at about 0.9 km, at the base of a weakly stable layer where some thin clouds could be identified. This level corresponds to the height of one of the two main peaks, with nearly the same intensity, of the radar–
Around midday (Fig. 2b) and midafternoon (Fig. 2c) only one prominent
3) Concluding remarks
In summary, the analysis of these two case studies shows ambiguity in the determination of the Zi from
4. Estimation of the CBL height with C2n
Two main algorithms to estimate the CBL height from UHF profiler data have been suggested by several researchers, as quoted in the introductory section. These algorithms are based on the entrainment-induced maximum of backscatter intensity, such as maximum value of SNR or
a. Maximum backscattered intensity method
This method, proposed by White (1993), simply assigns the CBL height as the level of
The maximum backscattered intensity method takes the primary
b. Median filtering method
This method is based on an increase in backscatter intensity in the same way as the maximum backscattered intensity method. However, a median filter is used to remove
Angevine et al. (1994) suggested two algorithms to find CBL height. In the first, a
Vertical profiles of UHF backscattered intensity and the CBL heights determined from the first median filtering method of Angevine et al. (1994) are shown in Fig. 4. The solid lines in each panel represent the
Vertical profiles of UHF-backscattered intensity and the CBL heights determined from the median filtering method of Dye et al. (1995) for the same case as Figs. 3 and 4 are shown in Fig. 5. In the case of Fig. 5a, with both elevated residual layer and CBL height, this method determined the lower
The median filtering methods of Angevine et al. (1994) and Dye et al. (1995) performed best when scattered fair weather cumulus clouds were present or vertical profiles of backscatter intensity had a single peak structure, but performed worst when deep clouds were persistently present over the UHF radar or vertical profiles of backscattered intensity had a double peak structure. These algorithms find a representative CBL height from several profiles of backscattered intensity observed during an hour. Consequently, these methods provide CBL height estimations of lower time resolution than the maximum backscattered intensity method, which can estimate its height from a single profile (in about 10 min).
5. Estimation of CBL height using C2n σ2w
The fourth method introduced here is a proposed improvement to the existing methods by making use of the UHF Doppler spectral width. The maximum backscattered intensity method and median filtering method were found to be incomplete in their estimations of CBL height when the backscattered intensity profile had a double peak, and the primary peak in each profile occurred in cloud layers or at the top of a residual layer rather than at the top of the mixed layer. In this paper, an algorithm is proposed to distinguish the peak caused by CBL height from other peaks due to either a cloud layer or a residual layer. This is done by using the variance of vertical air velocity measured by a UHF profiler.
The new method follows three steps to find the reference height using the
First, the primary and secondary peaks were selected in each
Second, a linear regression line of Eq. (4) was obtained by least square fitting between the preceding estimation of Z1 and 0.2Z1. The lower bound (0.2Z1) secures the only data in the mixed layer for the least square fitting. Therefore, the values of
Third, the zero heat flux height, Z0 was estimated by an extrapolation of the regression line as shown in Fig. 6. Therefore, the height of the
Figure 6 shows the vertical profiles of UHF-backscattered intensity and CBL height determined using
6. Estimation of diurnal variation of CBL height
Four methods, as previously mentioned, were compared and analyzed to examine their ability to estimate the diurnal variation of CBL height during a clear day and a cloudy day. In addition, the time resolution of the analyzed CBL heights was compared using the diurnal variations of the CBL heights obtained by the four different methods.
The CBL heights were estimated from the vertical profiles of UHF backscattered intensity on a clear day using four different methods. The diurnal variations of CBL height are shown in Fig. 7 for 19 June 1998. According to the strongest peak in the time–height cross section of
The diurnal variations of CBL heights derived from the maximum backscattered intensity method shown in Fig. 7a agree well with the rawinsonde-estimated CBL heights and also provided reasonable structure and evolution of the CBL during the growth of the CBL height. During the late afternoon between 1600 and 1750 LST, however, this method overestimated the CBL height when partial clouds were persistently present at 2.1 km and higher. Figures 7b and 7c show the diurnal variations of the CBL heights determined by the median filtering method of Angevine et al. (1994) and Dye et al. (1995), respectively. The results are similar to that of the CBL heights estimated by the maximum backscattered intensity method. The diurnal variations of the CBL heights estimated by the new method using
The diurnal variations of the CBL heights on a cloudy day estimated by four different methods are shown in Fig. 9. Considering both the variation of the strongest peak in the time–height plots of
7. Summary and conclusions
In the present study, the applicability of
The peaks in each
The maximum backscattered intensity method and median filtering method correctly estimated the CBL height when the
The new method developed in this study can estimate CBL height using
Acknowledgments
The TRAC experiment was mainly funded by the Institut National des Sciences de l'Univers (INSU), Météo-France and Electricité De France (EDF). Two authors (Kim and Heo) gratefully appreciate the financial support of the Korea Science and Engineering Foundation Grant KOSEF 985-0400-004-2.
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Vertical profiles of the virtual potential temperature (θυ), mixing ratio (q), virtual potential temperature gradient (dθυ/dz), and mean vertical gradient of potential refractivity (M2) from rawinsonde observations at (a) 0803 and (b) 1059 LST, and
Citation: Journal of Atmospheric and Oceanic Technology 20, 3; 10.1175/1520-0426(2003)020<0408:UOTDSW>2.0.CO;2
Vertical profiles of the virtual potential temperature (θυ), mixing ratio (q), virtual potential temperature gradient (dθυ/dz), and mean vertical gradient of potential refractivity (M2) from rawinsonde observations at (a) 0803 and (b) 1059 LST, and
Citation: Journal of Atmospheric and Oceanic Technology 20, 3; 10.1175/1520-0426(2003)020<0408:UOTDSW>2.0.CO;2
Vertical profiles of the virtual potential temperature (θυ), mixing ratio (q), virtual potential temperature gradient (dθυ/dz), and mean vertical gradient of potential refractivity (M2) from rawinsonde observations at (a) 0803 and (b) 1059 LST, and
Citation: Journal of Atmospheric and Oceanic Technology 20, 3; 10.1175/1520-0426(2003)020<0408:UOTDSW>2.0.CO;2
As in Fig. 1, except for (a) 0802, (b) 1119, and (c) 1403 LST on 29 Jun 1998. Vertical solid bars with the B and S characters in the leftmost panel represent a cloud layer and broken and scattered clouds, respectively
Citation: Journal of Atmospheric and Oceanic Technology 20, 3; 10.1175/1520-0426(2003)020<0408:UOTDSW>2.0.CO;2
As in Fig. 1, except for (a) 0802, (b) 1119, and (c) 1403 LST on 29 Jun 1998. Vertical solid bars with the B and S characters in the leftmost panel represent a cloud layer and broken and scattered clouds, respectively
Citation: Journal of Atmospheric and Oceanic Technology 20, 3; 10.1175/1520-0426(2003)020<0408:UOTDSW>2.0.CO;2
As in Fig. 1, except for (a) 0802, (b) 1119, and (c) 1403 LST on 29 Jun 1998. Vertical solid bars with the B and S characters in the leftmost panel represent a cloud layer and broken and scattered clouds, respectively
Citation: Journal of Atmospheric and Oceanic Technology 20, 3; 10.1175/1520-0426(2003)020<0408:UOTDSW>2.0.CO;2
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Citation: Journal of Atmospheric and Oceanic Technology 20, 3; 10.1175/1520-0426(2003)020<0408:UOTDSW>2.0.CO;2
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Citation: Journal of Atmospheric and Oceanic Technology 20, 3; 10.1175/1520-0426(2003)020<0408:UOTDSW>2.0.CO;2
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Citation: Journal of Atmospheric and Oceanic Technology 20, 3; 10.1175/1520-0426(2003)020<0408:UOTDSW>2.0.CO;2
Vertical profiles of the UHF backscatter intensity and CBL heights (asterisks) estimated by the maximum backscatter intensity method at (a) 0800 and (b) 1100 LST on 19 Jun, and (c) 0801, (d) 1121, and (e) 1401 LST on 29 Jun 1998. Parameters Zi denotes the CBL height determined by the gradient method of Sullivan et al. (1998) from rawinsonde observations
Citation: Journal of Atmospheric and Oceanic Technology 20, 3; 10.1175/1520-0426(2003)020<0408:UOTDSW>2.0.CO;2
Vertical profiles of the UHF backscatter intensity and CBL heights (asterisks) estimated by the maximum backscatter intensity method at (a) 0800 and (b) 1100 LST on 19 Jun, and (c) 0801, (d) 1121, and (e) 1401 LST on 29 Jun 1998. Parameters Zi denotes the CBL height determined by the gradient method of Sullivan et al. (1998) from rawinsonde observations
Citation: Journal of Atmospheric and Oceanic Technology 20, 3; 10.1175/1520-0426(2003)020<0408:UOTDSW>2.0.CO;2
Vertical profiles of the UHF backscatter intensity and CBL heights (asterisks) estimated by the maximum backscatter intensity method at (a) 0800 and (b) 1100 LST on 19 Jun, and (c) 0801, (d) 1121, and (e) 1401 LST on 29 Jun 1998. Parameters Zi denotes the CBL height determined by the gradient method of Sullivan et al. (1998) from rawinsonde observations
Citation: Journal of Atmospheric and Oceanic Technology 20, 3; 10.1175/1520-0426(2003)020<0408:UOTDSW>2.0.CO;2
As in Fig. 3, except for the median filtering method of Angevine et al. (1994). Solid lines represent the
Citation: Journal of Atmospheric and Oceanic Technology 20, 3; 10.1175/1520-0426(2003)020<0408:UOTDSW>2.0.CO;2
As in Fig. 3, except for the median filtering method of Angevine et al. (1994). Solid lines represent the
Citation: Journal of Atmospheric and Oceanic Technology 20, 3; 10.1175/1520-0426(2003)020<0408:UOTDSW>2.0.CO;2
As in Fig. 3, except for the median filtering method of Angevine et al. (1994). Solid lines represent the
Citation: Journal of Atmospheric and Oceanic Technology 20, 3; 10.1175/1520-0426(2003)020<0408:UOTDSW>2.0.CO;2
As in Fig. 3, except for the median filtering method of Dye et al. (1995). Circles indicate the
Citation: Journal of Atmospheric and Oceanic Technology 20, 3; 10.1175/1520-0426(2003)020<0408:UOTDSW>2.0.CO;2
As in Fig. 3, except for the median filtering method of Dye et al. (1995). Circles indicate the
Citation: Journal of Atmospheric and Oceanic Technology 20, 3; 10.1175/1520-0426(2003)020<0408:UOTDSW>2.0.CO;2
As in Fig. 3, except for the median filtering method of Dye et al. (1995). Circles indicate the
Citation: Journal of Atmospheric and Oceanic Technology 20, 3; 10.1175/1520-0426(2003)020<0408:UOTDSW>2.0.CO;2
As in Fig. 3, except for the new method using
Citation: Journal of Atmospheric and Oceanic Technology 20, 3; 10.1175/1520-0426(2003)020<0408:UOTDSW>2.0.CO;2
As in Fig. 3, except for the new method using
Citation: Journal of Atmospheric and Oceanic Technology 20, 3; 10.1175/1520-0426(2003)020<0408:UOTDSW>2.0.CO;2
As in Fig. 3, except for the new method using
Citation: Journal of Atmospheric and Oceanic Technology 20, 3; 10.1175/1520-0426(2003)020<0408:UOTDSW>2.0.CO;2
Time–height cross section of the refractive index structure parameter
Citation: Journal of Atmospheric and Oceanic Technology 20, 3; 10.1175/1520-0426(2003)020<0408:UOTDSW>2.0.CO;2
Time–height cross section of the refractive index structure parameter
Citation: Journal of Atmospheric and Oceanic Technology 20, 3; 10.1175/1520-0426(2003)020<0408:UOTDSW>2.0.CO;2
Time–height cross section of the refractive index structure parameter
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Citation: Journal of Atmospheric and Oceanic Technology 20, 3; 10.1175/1520-0426(2003)020<0408:UOTDSW>2.0.CO;2
(Continued)
Citation: Journal of Atmospheric and Oceanic Technology 20, 3; 10.1175/1520-0426(2003)020<0408:UOTDSW>2.0.CO;2
(Continued)
Citation: Journal of Atmospheric and Oceanic Technology 20, 3; 10.1175/1520-0426(2003)020<0408:UOTDSW>2.0.CO;2
Time–height cross section of
Citation: Journal of Atmospheric and Oceanic Technology 20, 3; 10.1175/1520-0426(2003)020<0408:UOTDSW>2.0.CO;2
Time–height cross section of
Citation: Journal of Atmospheric and Oceanic Technology 20, 3; 10.1175/1520-0426(2003)020<0408:UOTDSW>2.0.CO;2
Time–height cross section of
Citation: Journal of Atmospheric and Oceanic Technology 20, 3; 10.1175/1520-0426(2003)020<0408:UOTDSW>2.0.CO;2
As in Fig. 7, except for 29 Jun 1998
Citation: Journal of Atmospheric and Oceanic Technology 20, 3; 10.1175/1520-0426(2003)020<0408:UOTDSW>2.0.CO;2
As in Fig. 7, except for 29 Jun 1998
Citation: Journal of Atmospheric and Oceanic Technology 20, 3; 10.1175/1520-0426(2003)020<0408:UOTDSW>2.0.CO;2
As in Fig. 7, except for 29 Jun 1998
Citation: Journal of Atmospheric and Oceanic Technology 20, 3; 10.1175/1520-0426(2003)020<0408:UOTDSW>2.0.CO;2
(Continued)
Citation: Journal of Atmospheric and Oceanic Technology 20, 3; 10.1175/1520-0426(2003)020<0408:UOTDSW>2.0.CO;2
(Continued)
Citation: Journal of Atmospheric and Oceanic Technology 20, 3; 10.1175/1520-0426(2003)020<0408:UOTDSW>2.0.CO;2
(Continued)
Citation: Journal of Atmospheric and Oceanic Technology 20, 3; 10.1175/1520-0426(2003)020<0408:UOTDSW>2.0.CO;2
As in Fig. 8, except for 29 Jun 1998
Citation: Journal of Atmospheric and Oceanic Technology 20, 3; 10.1175/1520-0426(2003)020<0408:UOTDSW>2.0.CO;2
As in Fig. 8, except for 29 Jun 1998
Citation: Journal of Atmospheric and Oceanic Technology 20, 3; 10.1175/1520-0426(2003)020<0408:UOTDSW>2.0.CO;2
As in Fig. 8, except for 29 Jun 1998
Citation: Journal of Atmospheric and Oceanic Technology 20, 3; 10.1175/1520-0426(2003)020<0408:UOTDSW>2.0.CO;2
