RadxQpe expanded - Revision history

Jcdehart at 18:34, 9 February 2021

2021-02-09T18:34:47Z

Jcdehart: /* Elevated Terrain */

2021-02-02T15:55:53Z

Elevated Terrain

Jcdehart at 22:51, 27 January 2021

2021-01-27T22:51:06Z

Jcdehart: /* Overview */

2021-01-27T22:49:39Z

Overview

Jcdehart: /* Flowchart */

2021-01-26T23:32:33Z

Flowchart

Jcdehart at 23:32, 26 January 2021

2021-01-26T23:32:22Z

Jcdehart: /* Signal Quality */

2021-01-26T22:18:12Z

Signal Quality

Jcdehart at 22:17, 26 January 2021

2021-01-26T22:17:06Z

Jcdehart: /* Signal Quality */

2021-01-26T22:15:50Z

Signal Quality

Jcdehart: /* Signal Quality */

2021-01-26T22:12:14Z

Signal Quality

@@ Line 2: / Line 2: @@
 The goal of RadxQpe is to provide the best two-dimensional estimate of precipitation rates at ground level. To do so, RadxQpe must account for elevated terrain, areas of weak signal, and the height of the radar beam. This page will walk through how the application handles these factors to produce the end result.
-===== '''Elevated Terrain''' =====
+=== '''Elevated Terrain''' ===
 In certain regions, mountain ranges block radar beams at lower elevation angles, as shown in the example of a 0.5º elevation sweep from northern Taiwan below (left image). The white oval highlights weak reflectivity values in the middle of the east-west line of intense reflectivity values. The region of weak reflectivity corresponds to beam blockage by Taiwan's Central Mountain Range (fractional value; right image).
@@ Line 15: / Line 15: @@
 [[File:Rate_rhybrid_annotated2.png|550px]][[File:Qpe_rhybrid_annotated2.png|550px]]
-===== '''Signal Quality''' =====
+=== '''Signal Quality''' ===
 Factors that impact the signal quality include poor signal to noise ratios and the strength of the rain rate. If the input radar data includes the signal to noise ratio (SNR) as a variable, RadxQpe will use the [http://wiki.lrose.net/index.php/RadxQpe#Additional_parameters_to_edit minimum threshold] to determine if the data quality if sufficient or if data from a higher elevation angle is needed. If SNR doesn't exist, RadxQpe will calculate the SNR from the reflectivity field.
@@ Line 24: / Line 24: @@
 [[File:Rate_rhybrid2.png|550px]][[File:Qpe_rhybrid2.png|550px]]
-===== '''Radar Beam Height''' =====
+=== '''Radar Beam Height''' ===
 Due to refraction and curvature of the earth, the height of a radar beam increases with increasing range. Thus, at large distances from the radar, the 0.5º sweep is several km above the ground. Since RadxQpe aims to return the estimated ''surface'' precipitation, the user can set a [http://wiki.lrose.net/index.php/RadxQpe#Additional_parameters_to_edit maximum beam height] above which the precipitation rate will be set to 0.
@@ Line 31: / Line 31: @@
 [[File:Rate_rhybrid2.png|550px]][[File:Qpe_rhybrid2.png|550px]]
-===== '''Flowchart''' =====
+=== '''Flowchart''' ===
 A flowchart that describes the order of RadxQpe decisions from [http://wiki.lrose.net/index.php/RadxRate_equations#References Dixon et al. (2015)] is shown below.
 [[File:Qpe_flowchart.png|350px]]
-===== '''References''' =====
+=== '''References''' ===
 Dixon, M. J., J. W. Wilson, T. M. Weckwerth, D. Albo, and E. J. Thompson, 2015: A dual-polarization QPE method based on the NCAR particle ID algorithm: Description and preliminary results. 37th Conf. on Radar Meteorology, Norman, OK, Amer. Meteor. Soc., 9A.1. [https://ams.confex.com/ams/37RADAR/webprogram/Paper275705.html Link]

@@ Line 3: / Line 3: @@
 ===== '''Elevated Terrain''' =====
-In certain regions, mountain ranges block radar beams at lower elevation angles, as shown in the example of a 0.5º elevation sweep from northern Taiwan below (left image). The white oval highlights weak reflectivity values in the middle of the east-west line of intense reflectivity values. The region of weak reflectivity corresponds to beam blockage by Taiwan's Central Mountain Range, as shown in the beam blockage (fractional value; right image).
+In certain regions, mountain ranges block radar beams at lower elevation angles, as shown in the example of a 0.5º elevation sweep from northern Taiwan below (left image). The white oval highlights weak reflectivity values in the middle of the east-west line of intense reflectivity values. The region of weak reflectivity corresponds to beam blockage by Taiwan's Central Mountain Range (fractional value; right image).
 [[File:Rate_dbz_0pt5_annotated.png|550px]][[File:beame_0pt5.png|550px]]

@@ Line 5: / Line 5: @@
 In certain regions, mountain ranges block radar beams at lower elevation angles, as shown in the example of a 0.5º elevation sweep from northern Taiwan below (left image). The white oval highlights weak reflectivity values in the middle of the east-west line of intense reflectivity values. The region of weak reflectivity corresponds to beam blockage by Taiwan's Central Mountain Range, as shown in the beam blockage (fractional value; right image).
-[[File:Rate_dbz_0pt5_annotated.png|500px]][[File:beame_0pt5.png|500px]]
+[[File:Rate_dbz_0pt5_annotated.png|550px]][[File:beame_0pt5.png|550px]]
 However, radars often scan three-dimensional volumes and at a higher elevation angle of 1.5º, the band of intense reflectivity values in the oval is no longer discontinuous (left image) and the beam blockage is far weaker (right image).
-[[File:Rate_dbz_1pt5_annotated.png|500px]][[File:beame_1pt5.png|500px]]
+[[File:Rate_dbz_1pt5_annotated.png|550px]][[File:beame_1pt5.png|550px]]
 RadxQpe takes advantage of the three-dimensional radar volume to look at different elevation angles in regions where terrain exists to find to elevation angles closest to but above ground level. This process is done by linking to the output from RadxBeamBlock in the RadxQpe [http://wiki.lrose.net/index.php/RadxQpe#Important_parameters parameter file]. The default choice for the maximum fractional beam blockage is 0.25. While the estimated precipitation rate from lowest elevation angle in the RadxRate file (left image) is discontinuous, RadxQpe's estimate of surface precipitation (right image) includes the precipitation rates occurring above the Taiwanese mountain range.
-[[File:Rate_rhybrid_annotated2.png|500px]][[File:Qpe_rhybrid_annotated2.png|500px]]
+[[File:Rate_rhybrid_annotated2.png|550px]][[File:Qpe_rhybrid_annotated2.png|550px]]
 ===== '''Signal Quality''' =====
@@ Line 22: / Line 22: @@
 The two images below show the precipitation rate from RadxRate (left image; 0.5º elevation angle) and RadxQpe (right image). In the RadxRate image, the dark blue color (associated with precipitation rates less than 1 mm/hr) covers a large area, whereas the RadxQpe image shows far less coverage of the lightest precipitation rates (the minimum valid rate was 0.5 mm/hr for this example).
-[[File:Rate_rhybrid2.png|500px]][[File:Qpe_rhybrid2.png|500px]]
+[[File:Rate_rhybrid2.png|550px]][[File:Qpe_rhybrid2.png|550px]]
 ===== '''Radar Beam Height''' =====
@@ Line 29: / Line 29: @@
 The two images below show the precipitation rate from RadxRate (left image; 0.5º elevation angle) and RadxQpe (right image). In the example below, the maximum beam height was set to 4 km above mean sea level. All data beyond ~150 km has been removed due to this height requirement.
-[[File:Rate_rhybrid2.png|500px]][[File:Qpe_rhybrid2.png|500px]]
+[[File:Rate_rhybrid2.png|550px]][[File:Qpe_rhybrid2.png|550px]]
 ===== '''Flowchart''' =====

@@ Line 1: / Line 1: @@
 === '''Overview''' ===
-The goal of RadxQpe is to provide the best two-dimensional estimate of rainfall at ground level. To do so, RadxQpe must account for areas of weak signal, elevated terrain, and the height of the radar beam. This page will walk through how the application handles these factors to produce the end result.
+The goal of RadxQpe is to provide the best two-dimensional estimate of precipitation rates at ground level. To do so, RadxQpe must account for elevated terrain, areas of weak signal, and the height of the radar beam. This page will walk through how the application handles these factors to produce the end result.
 ===== '''Elevated Terrain''' =====
@@ Line 7: / Line 7: @@
 [[File:Rate_dbz_0pt5_annotated.png|500px]][[File:beame_0pt5.png|500px]]
-However, radars often scan three-dimensional volumes and at the higher elevation angle of 1.5º, the band of intense reflectivity values in the oval is no longer discontinuous (left image) and the beam blockage is far weaker (right image).
+However, radars often scan three-dimensional volumes and at a higher elevation angle of 1.5º, the band of intense reflectivity values in the oval is no longer discontinuous (left image) and the beam blockage is far weaker (right image).
 [[File:Rate_dbz_1pt5_annotated.png|500px]][[File:beame_1pt5.png|500px]]
-RadxQpe takes advantage of the three-dimensional radar volume to look at different elevation angles in regions where terrain exists to find to elevation angles closest to ground level. This process is done by linking to the output from RadxBeamBlock in the RadxQpe [http://wiki.lrose.net/index.php/RadxQpe#Important_parameters parameter file]. While the estimated precipitation rate from lowest elevation angle in the RadxRate file (left image) is discontinuous, RadxQpe's estimate of surface precipitation (right image) displays the precipitation rates occurring above the Taiwanese mountain range.
+RadxQpe takes advantage of the three-dimensional radar volume to look at different elevation angles in regions where terrain exists to find to elevation angles closest to but above ground level. This process is done by linking to the output from RadxBeamBlock in the RadxQpe [http://wiki.lrose.net/index.php/RadxQpe#Important_parameters parameter file]. The default choice for the maximum fractional beam blockage is 0.25. While the estimated precipitation rate from lowest elevation angle in the RadxRate file (left image) is discontinuous, RadxQpe's estimate of surface precipitation (right image) includes the precipitation rates occurring above the Taiwanese mountain range.
 [[File:Rate_rhybrid_annotated2.png|500px]][[File:Qpe_rhybrid_annotated2.png|500px]]
 ===== '''Signal Quality''' =====
-Factors that impact the signal quality include poor signal to noise ratios and the strength of the rain rate. If the radar data being processed includes the signal to noise ratio (SNR) as a variable, RadxQpe will use the [http://wiki.lrose.net/index.php/RadxQpe#Additional_parameters_to_edit minimum threshold] to determine if the data quality if sufficient or if data from a higher elevation angle is needed. If SNR doesn't exist, RadxQpe will calculate it from the dBZ field.
+Factors that impact the signal quality include poor signal to noise ratios and the strength of the rain rate. If the input radar data includes the signal to noise ratio (SNR) as a variable, RadxQpe will use the [http://wiki.lrose.net/index.php/RadxQpe#Additional_parameters_to_edit minimum threshold] to determine if the data quality if sufficient or if data from a higher elevation angle is needed. If SNR doesn't exist, RadxQpe will calculate the SNR from the reflectivity field.
 RadxQpe also allows the user to set the [http://wiki.lrose.net/index.php/RadxQpe#Additional_parameters_to_edit minimum valid precipitation rate] (mm/hr). Any precipitation rates below this threshold will be set to 0.
@@ Line 25: / Line 25: @@
 ===== '''Radar Beam Height''' =====
-Due to refraction and curvature of the earth, the height of a radar beam increases with increasing range. Thus, at large distances, the 0.5º sweep is several km above the ground. Since RadxQpe aims to return the estimated ''surface'' precipitation, the user can set a [http://wiki.lrose.net/index.php/RadxQpe#Additional_parameters_to_edit maximum beam height] above which the precipitation rate will be set to 0.
+Due to refraction and curvature of the earth, the height of a radar beam increases with increasing range. Thus, at large distances from the radar, the 0.5º sweep is several km above the ground. Since RadxQpe aims to return the estimated ''surface'' precipitation, the user can set a [http://wiki.lrose.net/index.php/RadxQpe#Additional_parameters_to_edit maximum beam height] above which the precipitation rate will be set to 0.
 The two images below show the precipitation rate from RadxRate (left image; 0.5º elevation angle) and RadxQpe (right image). In the example below, the maximum beam height was set to 4 km above mean sea level. All data beyond ~150 km has been removed due to this height requirement.

@@ Line 34: / Line 34: @@
 A flowchart that describes the order of RadxQpe decisions from [http://wiki.lrose.net/index.php/RadxRate_equations#References Dixon et al. (2015)] is shown below.
-[[File:Qpe_flowchart.png|500px]]
+[[File:Qpe_flowchart.png|350px]]
 ===== '''References''' =====
 Dixon, M. J., J. W. Wilson, T. M. Weckwerth, D. Albo, and E. J. Thompson, 2015: A dual-polarization QPE method based on the NCAR particle ID algorithm: Description and preliminary results. 37th Conf. on Radar Meteorology, Norman, OK, Amer. Meteor. Soc., 9A.1. [https://ams.confex.com/ams/37RADAR/webprogram/Paper275705.html Link]

← Older revision		Revision as of 23:32, 26 January 2021
Line 30:		Line 30:

	[[File:Rate_rhybrid2.png\|500px]][[File:Qpe_rhybrid2.png\|500px]]		[[File:Rate_rhybrid2.png\|500px]][[File:Qpe_rhybrid2.png\|500px]]
		+
		+	===== '''Flowchart''' =====
		+	A flowchart that describes the order of RadxQpe decisions from [http://wiki.lrose.net/index.php/RadxRate_equations#References Dixon et al. (2015)] is shown below.
		+
		+	[[File:Qpe_flowchart.png\|500px]]
		+
		+	===== '''References''' =====
		+	Dixon, M. J., J. W. Wilson, T. M. Weckwerth, D. Albo, and E. J. Thompson, 2015: A dual-polarization QPE method based on the NCAR particle ID algorithm: Description and preliminary results. 37th Conf. on Radar Meteorology, Norman, OK, Amer. Meteor. Soc., 9A.1. [https://ams.confex.com/ams/37RADAR/webprogram/Paper275705.html Link]

@@ Line 22: / Line 22: @@
 The two images below show the precipitation rate from RadxRate (left image; 0.5º elevation angle) and RadxQpe (right image). In the RadxRate image, the light green color (associated with precipitation rates between 0-3 mm/hr) covers a large area, whereas the RadxQpe image shows far less coverage of the lightest precipitation rates (the minimum valid rate was 0.5 mm/hr for this example).
-[[File:Rate_rhybrid.png|500px]][[File:Qpe_rhybrid.png|500px]]
+[[File:Rate_rhybrid2.png|500px]][[File:Qpe_rhybrid.png|500px]]
 ===== '''Radar Beam Height''' =====

← Older revision		Revision as of 22:12, 26 January 2021
Line 21:		Line 21:

	The two images below show the precipitation rate from RadxRate (left image; 0.5º elevation angle) and RadxQpe (right image). In the RadxRate image, the light green color (associated with precipitation rates between 0-3 mm/hr) covers a large area, whereas the RadxQpe image shows far less coverage of the lightest precipitation rates (the minimum valid rate was 0.5 mm/hr for this example).		The two images below show the precipitation rate from RadxRate (left image; 0.5º elevation angle) and RadxQpe (right image). In the RadxRate image, the light green color (associated with precipitation rates between 0-3 mm/hr) covers a large area, whereas the RadxQpe image shows far less coverage of the lightest precipitation rates (the minimum valid rate was 0.5 mm/hr for this example).
		+
		+	[[File:Rate_rhybrid.png\|500px]][[File:Qpe_rhybrid.png\|500px]]

	===== '''Radar Beam Height''' =====		===== '''Radar Beam Height''' =====