4,107 Hits in 2.5 sec

Overfishing of Inland Waters

2005 BioScience  
doi:10.1641/0006-3568(2005)055[1041:ooiw];2 fatcat:5df6ll5kd5bmxffryryhhay6wi

Fast approximate calculation of multiply scattered lidar returns

Robin J. Hogan
2006 Applied Optics  
and P j s j in memory such that the weighted summations become ͑P j s 2 j ͒ ← ͑P j s 2 j ͒ ϩ ⌬P j ϫ ⌬s 2 j , (26) and similarly for P j 2 j and P j s j .  ...  2 ϭ x i 2 ϩ ͑ x,i 2 ϩ x,i 2 ͒͑r j Ϫ r i͒ 2 ϩ 2x i x,i͑ r j Ϫ r i͒ , (20) ⌬P s,j ϭ ␣ i ⌬r, (21) ⌬s 2 s,j ϭ l 2 r j 2 ϩ ⌰ i 2 ͑ r j Ϫ r i͒ 2 , (22) ⌬ 2 s,j ϭ l 2 ϩ ⌰ i 2 , (23) ⌬s s,j ϭ l 2 r j ϩ ⌰ i 2 ͑  ... 
doi:10.1364/ao.45.005984 pmid:16926887 fatcat:cn2ippewr5cldjyqyibyju6joy

Verification of cloud-fraction forecasts

Robin J. Hogan, Ewan J. O'Connor, Anthony J. Illingworth
2009 Quarterly Journal of the Royal Meteorological Society  
J. HOGAN ET AL.  ...  J.  ... 
doi:10.1002/qj.481 fatcat:uffbyrsj7fdozlwwm562bpyr3q

Asperitas - a newly identified cloud supplementary feature

R. Giles Harrison, Gavin Pretor-Pinney, Graeme J. Marlton, Graeme D. Anderson, Daniel J. Kirshbaum, Robin J. Hogan
2017 Weather  
Cloud images obtained through a crowd-sourced international observing network suggest a cloud variety that has hitherto not been explicitly classified. This cloud feature shows a roughened base, which, under some solar illumination conditions, provides a particularly dramatic appearance. The growing body of photographic observations have led the World Meteorological Organisation to consider adding 'asperitas' to the 2017 edition of the International Cloud Atlas as a new form of supplementary
more » ... ud feature. We compare reported sightings with available meteorological data to investigate the conditions that give rise to this newly recognised cloud description. 1 Cirrus dominated by irregularly curved filaments of ice, giving an entangled appearance. 2 from the Latin noun meaning roughness
doi:10.1002/wea.2996 fatcat:nnqm66xdwfgq7atv2q5rjszj2m

Rainfall nowcasting by combining radars, microwave links and rain gauges [article]

Blandine Bianchi, Peter Jan van Leeuwen, Robin J. Hogan, Alexis Berne
2018 arXiv   pre-print
A similar assumption for radar observations has been made by Hogan (2007) .  ...  The first quadrant of the covariance matrix of the state is given by B ij = B ii exp − d ij d 0 , (9) where B ii is the radar error and d ij is the distance between the pixel i and j, with i, j = 1, ..  ... 
arXiv:1810.11811v1 fatcat:sukzhsipc5bdfjmtzyy4odvxci

Copula-based synthetic data augmentation for machine- learning emulators

David Meyer, Thomas Nagler, Robin J. Hogan
2021 Geoscientific Model Development  
., 2021; Hogan and Matricardi, 2020) .  ...  For τ g we use a constant value of 1.7 determined by minimizing the absolute error between profiles computed with this simple model and the comprehensive atmospheric radiation scheme ecRad (Hogan and  ... 
doi:10.5194/gmd-14-5205-2021 fatcat:at6fzn7ijrfnrh27kuiwexgr6a

The Capacitance of Pristine Ice Crystals and Aggregate Snowflakes

Christopher David Westbrook, Robin J. Hogan, Anthony J. Illingworth
2008 Journal of the Atmospheric Sciences  
Forbes and Hogan 2006) . Method The simplest Monte Carlo model for solving (1) runs as follows. A random walker is placed on a large sphere, radius R ∞ .  ... 
doi:10.1175/2007jas2315.1 fatcat:372lp6jzn5dbtk67tlrfdwhsci

Stratocumulus Liquid Water Content from Dual-Wavelength Radar

Robin J. Hogan, Nicolas Gaussiat, Anthony J. Illingworth
2005 Journal of Atmospheric and Oceanic Technology  
A technique is described to retrieve stratocumulus liquid water content (LWC) using the differential attenuation measured by vertically pointing radars at 35 GHz and 94 GHz. Millimeter-wave attenuation is proportional to LWC and increases with frequency, so LWC can be derived without the need to make any assumptions on the nature of the droplet size distribution. There is also no need for the radars to be well calibrated. A significant advantage over many radar techniques in stratocumulus is
more » ... t the presence of drizzle drops (those with a diameter larger than around 50 µm) does not affect the retrieval, even though such drops may dominate the radar signal. It is important, however, that there are not significant numbers of drops larger than 600 µm which scatter outside the Rayleigh regime at 94 GHz. We use a lidar ceilometer to locate cloud base in the presence of drizzle falling below the cloud. An accuracy of around 0.04 g m −3 is achievable with averaging over one minute and 150 m (two range gates), but for the previously suggested frequency pair 10 GHz and 35 GHz, the corresponding accuracy would be considerably worse at 0.34 g m −3 . We first simulate the retrieval of LWC using aircraft-measured size spectra taken from a profile through marine stratocumulus. Results are then presented from two case studies, one using two cloud radars at Chilbolton in Southern England, and another using the Cloud Profiling Radar System at the Atmospheric Radiation Measurement site in Oklahoma. Liquid water path from the technique was found to be in good agreement with the values obtained from microwave radiometers, with the difference between the two being close to the accuracy of the radiometer retrieval. In the case of wellmixed stratocumulus the profiles were close to adiabatic.
doi:10.1175/jtech1768.1 fatcat:lbe72kzbzzcrhk3j2qg2lks2sq

Fast Reverse-Mode Automatic Differentiation using Expression Templates in C++

Robin J. Hogan
2014 ACM Transactions on Mathematical Software  
ACM Reference Format: Robin J. Hogan. 2014. Fast reverse-mode automatic differentiation using expression templates in C++. ACM  ...  These methods make repeated estimates of x, at which they require not only the value of J but also the vector of gradients ∂ J/∂x in order to know in which direction to search next.  ...  The third algorithm uses the Photon Variance-Covariance (PVC) method of Hogan [2008] and computes the contribution to the measured signal from light that has been scattered multiple times, but only by  ... 
doi:10.1145/2560359 fatcat:x7miqimrq5deta45vmfwdvtkqm

Combined CloudSat-CALIPSO-MODIS retrievals of the properties of ice clouds

Julien Delanoë, Robin J. Hogan
2010 Journal of Geophysical Research  
(d, g, and j) The effect of assimilating the infrared radiances at 10 mm and the difference in radiance between 8 mm and 12 mm when S is assumed constant.  ...  Stein et al., A comparison between different retrieval methods for ice cloud properties using data from the CloudSat and A-Train satellites, manuscript in preparation, 2010; J.  ... 
doi:10.1029/2009jd012346 fatcat:kswytxda3zbk7e7z5d4o7ukqai

Comparison of ECMWF Winter-Season Cloud Fraction with Radar-Derived Values

Robin J. Hogan, Christian Jakob, Anthony J. Illingworth
2001 Journal of applied meteorology (1988)  
The same dataset was used by Hogan and Illingworth (2000) to characterize the degree of cloud overlap for use in GCMs.  ...  From around 14 hours of in situ aircraft measurements in mid-latitude cirrus, Hogan and Illingworth (1999b) derived the following relationship between 94-GHz radar reflectivity (Z 94 ) and IWC: log 10  ... 
doi:10.1175/1520-0450(2001)040<0513:coewsc>;2 fatcat:movy5rawhncqxdsdzhyzhnd2ae

Mean radiant temperature from global-scale numerical weather prediction models

Claudia Di Napoli, Robin J. Hogan, Florian Pappenberger
2020 International journal of biometeorology  
Modelling cloud fraction and cloud types, for instance, is difficult and makes predicting radiation still a demanding task although significant improvements have been achieved (Hogan et al. 2009; Hogan  ...  As described in the "Introduction", radiation quantities are stored as accumulated fluxes, i.e. as the energy that has passed through a square metre of a flat horizontal plane (units of J m −2 or W m −  ... 
doi:10.1007/s00484-020-01900-5 pmid:32274575 fatcat:wwqmvsermba3tc3opcyx7nqgka

Improved rain rate and drop size retrievals from airborne Doppler radar

Shannon L. Mason, J. Christine Chiu, Robin J. Hogan, Lin Tian
2017 Atmospheric Chemistry and Physics  
Edited by: Timothy J. Dunkerton Reviewed by: Alain Protat and two anonymous referees  ...  Multiple scattering effects on radar and lidar backscatter can be estimated within CAPTIVATE using Hogan (2008) .  ...  Additionally, profiles of retrieved variables can be represented smoothly as a set of cubic spline basis functions (Hogan, 2007, and Sect. 2.3 .3).  ... 
doi:10.5194/acp-17-11567-2017 fatcat:q3be4p6uibhevplngvzy6tn7tm

A method to diagnose boundary-layer type using Doppler lidar

Natalie J. Harvey, Robin J. Hogan, Helen F. Dacre
2013 Quarterly Journal of the Royal Meteorological Society  
J. R. Meteorol. Soc. 139: 1681-1693 (2013)  ...  This is similar to the signature of decoupled stratocumulus cloud observed by Hogan et al. (2009) .  ... 
doi:10.1002/qj.2068 fatcat:mma7xob73vg6fbpnoka6mviyje

Parameterizing Ice Cloud Inhomogeneity and the Overlap of Inhomogeneities Using Cloud Radar Data

Robin J. Hogan, Anthony J. Illingworth
2003 Journal of the Atmospheric Sciences  
al. 2001) , and cloud overlap (Hogan and Illingworth 2000) .  ...  Attenuation by the ice clouds themselves is negligible (Hogan and Illingworth 1999) .  ... 
doi:10.1175/1520-0469(2003)060<0756:piciat>;2 fatcat:zs6c4jrz5fhnhjoilvbe6mqpcu
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