Detection and Analysis of Microfronts and Associated Coherent Events Using Localized Transforms

Gamage, Nimal; Hagelberg, C. R.

doi:10.1175/1520-0469(1993)050<0750:daaoma>2.0.co;2

Cited by 115 publications

(66 citation statements)

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“…The WCT transform was defined by Gamage and Hagelberg (1993) as a mean of detecting step changes in a signal. It is based on the compound step function, the Haar function h, defines as…”

Section: Methodsmentioning

confidence: 99%

A robust method to determine global distribution of atmospheric boundary layer top from COSMIC GPS RO measurements

Ratnam

Basha

2010

Atmospheric Science Letters

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In this study, we introduce a robust method for precise determination of atmospheric boundary layer (ABL) top from COSMIC global positioning system radio occultation measurements. We apply a wavelet covariance transform to compute the convolution of COSMIC-observed bending angle/refractivity profile with a Haar function and use the maximum covariance to identify the ABL top, making detection of even small transitions possible. Results obtained were compared with radiosonde N profiles for verification of the ABL top. This procedure developed was used to study the global distribution of ABL top with special reference to the inter-tropical convergence zone.

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“…The WCT transform was defined by Gamage and Hagelberg (1993) as a mean of detecting step changes in a signal. It is based on the compound step function, the Haar function h, defines as…”

Section: Methodsmentioning

confidence: 99%

A robust method to determine global distribution of atmospheric boundary layer top from COSMIC GPS RO measurements

Ratnam

Basha

2010

Atmospheric Science Letters

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“…In this subset, only HSRL data within 45 min of the CALIOP closest point of approach were considered, which is slightly larger than the 30 min criterion used by Mona et al (2009). Furthermore, because clouds are highly variable in the atmosphere both HSRL and CALIOP data were screened for clouds at all altitudes using both the CALIOP VFM and HSRL cloud detection routine (detected as sharp gradients in the raw signals using a three point Haar wavelet covariance transform, Gamage and Hagelberg, 1993), as well as a manual inspection to ensure that only cloud-free profiles were used in the comparison. A total of twenty two cases (eight nighttime and fourteen daytime) was found to meet all of these selection criteria.…”

Section: Altitude Dependence Of the Caliop 532 Nm Total Attenuated Bamentioning

confidence: 99%

Assessment of the CALIPSO Lidar 532 nm attenuated backscatter calibration using the NASA LaRC airborne High Spectral Resolution Lidar

et al. 2011

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To better assess the range of conditions under which CALIOP data products are produced, these validation flights were conducted under both daytime and nighttime lighting conditions, in multiple seasons, and over a large range of latitudes and aerosol and cloud conditions. This paper presents a quantitative assessment of the CALIOP 532 nm calibration (through the 532 nm total attenuated backscatter) using internally calibrated airborne HSRL underflight data and is the most extensive study of CALIOP 532 nm calibration. Results show that HSRL and CALIOP 532 nm total attenuated backscatter agree on average within 2.7% ± 2.1% (CALIOP lower) at night and within 2.9% ± 3.9% (CALIOP lower) during the day, demonstrating the accuracy of the CALIOP 532 nm calibration algorithms. Additionally, comparisons with HSRL show consistency of the CALIOP calibration before and after the laser switch in 2009 as well as improvements in the daytime version 3.01 calibration scheme compared with the version 2 calibration scheme. Potential biases and uncertainties in the methodology relevant to validating satellite lidar measurements with an airborne lidar system are Correspondence to: R. R. Rogers (raymond.r.rogers@nasa.gov) discussed and found to be less than 4.5% ± 3.2% for this validation effort with HSRL. Results from this study are also compared with prior assessments of the CALIOP 532 nm attenuated backscatter calibration.

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“…Mahrt (1991) firstly introduced WT into atmospheric sciences when eddy asymmetry in the sheared heated boundary layer was studied. In recent years, WT has been widely used in a series of fields of atmospheric sciences, for instance, analyzing low-level cold fronts (Damage and Blumen, 1993), coherent structures at the atmosphere-forest interface (Gao and Li, 1993), microfronts and associated coherent events (Gamage and Hagelberg, 1993), rainfall spatial structure (Kumar and Foufoula-Georgiou, 1993), dispersion of mixed Rossby-gravity waves in a reduced gravity equatorial model (Meyers et al, 1993), period-doubling and time-frequency localization in the satellite infrared radiance data (Weng and Lau, 1994), vertical structure of atmospheric gravity waves (Sato and Yamada, 1994), interannual variability of sea surface temperature (SST) (Mak, 1995), a proxy paleoclimate time series and monthly mean surface temperature in the Northern Hemisphere (Lau and Weng, 1995), interannual and decadal variations of annual rainfall in North China (Hu, 1996), and so on.…”

Section: Wavelet Transform (Wt)mentioning

confidence: 99%

Wavelet Analysis of Summer Rainfall over North China and India and SOI Using 1891-1992 Data

Nitta

1996

Journal of the Meteorological Society of Japan

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Localization of interannual and decadal variations of summer rainfall in North China and India and seasonal mean Southern Oscillation Index (SOI) from , and the favored time scales of the significant correlations among them are investigated with the wavelet transform (WT) analysis method. Strong localization and non-stationary evolution in the interannual and decadal variations of the rainfall in North China and India are demonstrated. The dominating time scales in the rainfall variations in North China and India are mainly located in two time scale bands: shorter than 10 years, and 14-28 years. The correlations between the rainfall variations in North China and India are time-scale dependent. The significant positive correlations are concentrated in two time-scale bands: shorter than 7 years and longer than 14 years. The correlations are insignificant on time scales of 7-14 years.El Nino and Southern Oscillation (ENSO) cycle is a nonstationary process. The dominant time scales for the variation of SOI are shorter than 5-7 years, and the decadal variations are obvious in 1891-1915 and 1970-1992. There is strong interaction between the Indian summer monsoon and the ENSO cycle. The significant positive correlations are mainly focused on the time scales shorter than 24-30 years, and the significant negative correlations on time scales longer than 40 years in summer and winter SOI cases. The correlation between the rainfall variations in North China and the ENSO cycle in various seasons are less significant, more scattered and complex, but there are some similarities in the correlation pattern compared with that of India, especially in the shorter time scales.The calculation shows that the summer rainfall variations in North China and India at different time scales are related with different general circulation anomalous patterns in middle and high latitudes of Eurasia and the western Pacific. The correlation patterns over Eurasia and the western Pacific between the summer rainfall variations in North China or India and the geopotential height at 500hPa are similar to the correlation patterns between the geopotential height and the WT results of the rainfall on time scales of about 5 years, but different from those on time scales of about 11 years.Therefore, the similar behavior between the rainfall variations in North China and India may be caused by the similar associations between the rainfall variations and the ENSO cycle and the general circulation anomalies in middle and high latitudes over Eurasia and the western Pacific, and the difference may be related to the different character of these associations.

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Detection and Analysis of Microfronts and Associated Coherent Events Using Localized Transforms

Cited by 115 publications

References 0 publications

A robust method to determine global distribution of atmospheric boundary layer top from COSMIC GPS RO measurements

A robust method to determine global distribution of atmospheric boundary layer top from COSMIC GPS RO measurements

Assessment of the CALIPSO Lidar 532 nm attenuated backscatter calibration using the NASA LaRC airborne High Spectral Resolution Lidar

Wavelet Analysis of Summer Rainfall over North China and India and SOI Using 1891-1992 Data

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