Deadtime correction in PollyNET

[ZPYin]

Below is the MATLAB code to show how to use PollyNET deadtime correction scheme:

pollyDTCor.m is necessary for running the scripts below. Please download it here and add it into your MATLAB search path.

clc; close all;

%% initialization
pollyDataFile = 'D:\Data\PollyXT\pollyxt_noa\data_zip\202010\2020_10_01_Thu_NOA_18_00_31.nc';   % absolute path of polly data
deadtimeConfig1 = 3;   % deadtime for non-paralyzable deadtime correction. (ns)

%% read data
rawSig = double(ncread(pollyDataFile, 'raw_signal'));
deadtimeConfig2 = ncread(pollyDataFile, 'deadtime_polynomial');
mShots = double(ncread(pollyDataFile, 'measurement_shots'));
heightRes = double(ncread(pollyDataFile, 'measurement_height_resolution') * 0.15);
channelID_532FR = 5;

%% deadtime correction

% non-paralyzable model
sigDTCor1 = pollyDTCor(rawSig, mShots, heightRes, ...
    'flagDeadTimeCorrection', true, ...
    'deadtimeCorrectionMode', 2, ...
    'deadtimeParams', deadtimeConfig1 * ones(1, size(rawSig, 1)));

% paralyzable model
sigDTCor2 = pollyDTCor(rawSig, mShots, heightRes, ...
    'flagDeadTimeCorrection', true, ...
    'deadtime', deadtimeConfig2, ...
    'deadtimeCorrectionMode', 1);

%% data visualization
figure('Position', [0, 10, 300, 400], 'Units', 'Pixels', 'Color', 'w');

p1 = semilogx(squeeze(sum(rawSig(channelID_532FR, :, :), 3)), 1:size(rawSig, 2), '-k', 'Linewidth', 2, 'DisplayName', 'raw signal'); hold on;
p2 = semilogx(squeeze(sum(sigDTCor1(channelID_532FR, :, :), 3)), 1:size(rawSig, 2), '--g', 'Linewidth', 2, 'DisplayName', sprintf('\\tau: %4.1f ns', deadtimeConfig1)); hold on;
p3 = semilogx(squeeze(sum(sigDTCor2(channelID_532FR, :, :), 3)), 1:size(rawSig, 2), '--r', 'Linewidth', 2, 'DisplayName', '5-order polymonial'); hold on;

xlabel('Lidar signal (photon count)');
ylabel('Bin index');

xlim([1e5, 1e6]);
ylim([250, 400]);

set(gca, 'XMinorTick', 'on', 'YMinorTick', 'on', 'Box', 'on', 'Layer', 'Top', 'Linewidth', 2);

legend([p1, p2, p3], 'Location', 'NorthEast');

Below is the comparison plot for deadtime corrected profiles with non-paralyzable model (green dashed line) and paralyzable model (red dashed line):

For details of different deadtime correction schemes, please refer to the technical paper of Engelmann., R. et al (2016) (Section 2.3)