Implication of low intensity rain spectra (R≤1mm/h) in the variability of Z-R relationship linked to the microphysical processes of precipitation: Size-controlled, number-controlled and mixed control of drops

Bamba, Bakary; Koffi, Augustin Kadjo; Brahima, Koné; Kacou, Modeste; Bamba, Ibrahima; Zahiri, Eric-Pascal; Ochou, Abé Delfin

Volume 46, Issue 3, September 2025, Pages 563–582

Implication of low intensity rain spectra (R≤1mm/h) in the variability of Z-R relationship linked to the microphysical processes of precipitation: Size-controlled, number-controlled and mixed control of drops

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@article{IJIAS-25-238-11,
author = {Bakary Bamba and Augustin Kadjo Koffi and Koné Brahima and Modeste Kacou and Ibrahima Bamba and Eric-Pascal Zahiri and Abé Delfin Ochou},
title = {{Implication of low intensity rain spectra (R≤1mm/h) in the variability of Z-R relationship linked to the microphysical processes of precipitation: Size-controlled, number-controlled and mixed control of drops}},
journal = {International Journal of Innovation and Applied Studies},
volume = {46},
year = {2025},
pages = {563--582},
issue = {3},
number = {3},
issn = {2028-9324},
url = {http://www.ijias.issr-journals.org/abstract.php?article=IJIAS-25-238-11},
abstract_html_url = {http://www.ijias.issr-journals.org/abstract.php?article=IJIAS-25-238-11},
pdf_url = {http://www.issr-journals.org/links/papers.php?journal=ijias&application=pdf&article=IJIAS-25-238-11},
document_type={Article},
source={www.issr-journals.org}
}

TY  - JOUR
ID  - 
TI  - Implication of low intensity rain spectra (R≤1mm/h) in the variability of Z-R relationship linked to the microphysical processes of precipitation: Size-controlled, number-controlled and mixed control of drops
AU  - Bakary Bamba
AU  - Augustin Kadjo Koffi
AU  - Koné Brahima
AU  - Modeste Kacou
AU  - Ibrahima Bamba
AU  - Eric-Pascal Zahiri
AU  - Abé Delfin Ochou
PY  - 2025
VL  - 46
IS  - 3
SP  - 563
EP  - 582
JO  - International Journal of Innovation and Applied Studies
T2  - International Journal of Innovation and Applied Studies
SN  - 20289324
UR  - http://www.ijias.issr-journals.org/abstract.php?article=IJIAS-25-238-11
AB  - Understanding the necessary relationship between the radar reflectivity factor Z and the rain rate R is still important today and constitutes an interesting challenge for the scientific community. Despite this interest and the advances already obtained in this field, understanding the variability of this Z-R law is not yet trivial. This work therefore consists of studying the implication of rain spectra at low intensities R≤1mm/h in this variability. Thus, from a large historical database of raindrop size distribution (DSD) acquired in tropical Africa, we have shown that rain spectra R≤1mm/h lead to high values of the coefficients A and b of the Z-R power relationship. However, the variability of pre-factor A is pronounced in agreement with those of the NT and D0/NT parameters of the DSD; while the exponent b remains quasi-constant in such rainy samples, independently of their percentage. Establishing the link between the observation parameters D0, NT and D0/NT of the DSD and the pre-factor A of the Z-R relationship made it possible to arrive at close power relationships D0 – A, NT – A and D0/NT – A corresponding respectively to the microphysical modes «D0 constant, NT variable», «D0 variable, NT constant» and «D0 variable, NT variable». The last microphysical condition seems to be more suited to the power relationship A – α where α, is the pre-factor of the power relationship D0/NT – R found in the literature.
ER  -

TY  - JOUR
ID  - 
TI  - Implication of low intensity rain spectra (R≤1mm/h) in the variability of Z-R relationship linked to the microphysical processes of precipitation: Size-controlled, number-controlled and mixed control of drops
AU  - Bakary Bamba
AU  - Augustin Kadjo Koffi
AU  - Koné Brahima
AU  - Modeste Kacou
AU  - Ibrahima Bamba
AU  - Eric-Pascal Zahiri
AU  - Abé Delfin Ochou
PY  - 2025
VL  - 46
IS  - 3
SP  - 563
EP  - 582
JO  - International Journal of Innovation and Applied Studies
SN  - 20289324
AB  - 
Understanding the necessary relationship between the radar reflectivity factor Z and the rain rate R is still important today and constitutes an interesting challenge for the scientific community. Despite this interest and the advances already obtained in this field, understanding the variability of this Z-R law is not yet trivial. This work therefore consists of studying the implication of rain spectra at low intensities R≤1mm/h in this variability. Thus, from a large historical database of raindrop size distribution (DSD) acquired in tropical Africa, we have shown that rain spectra R≤1mm/h lead to high values of the coefficients A and b of the Z-R power relationship. However, the variability of pre-factor A is pronounced in agreement with those of the NT and D0/NT parameters of the DSD; while the exponent b remains quasi-constant in such rainy samples, independently of their percentage. Establishing the link between the observation parameters D0, NT and D0/NT of the DSD and the pre-factor A of the Z-R relationship made it possible to arrive at close power relationships D0 – A, NT – A and D0/NT – A corresponding respectively to the microphysical modes «D0 constant, NT variable», «D0 variable, NT constant» and «D0 variable, NT variable». The last microphysical condition seems to be more suited to the power relationship A – α where α, is the pre-factor of the power relationship D0/NT – R found in the literature.
ER  -

RT Journal Article
ID IJIAS-25-238-11
A1 Bakary Bamba
A1 Augustin Kadjo Koffi
A1 Koné Brahima
A1 Modeste Kacou
A1 Ibrahima Bamba
A1 Eric-Pascal Zahiri
A1 Abé Delfin Ochou
YR 2025
T1 Implication of low intensity rain spectra (R≤1mm/h) in the variability of Z-R relationship linked to the microphysical processes of precipitation: Size-controlled, number-controlled and mixed control of drops
JF International Journal of Innovation and Applied Studies

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Bakary Bamba¹, Augustin Kadjo Koffi², Koné Brahima³, Modeste Kacou⁴, Ibrahima Bamba⁵, Eric-Pascal Zahiri⁶, and Abé Delfin Ochou⁷

¹ Laboratoire de Physique de l’Atmosphère et de Mécanique des Fluides, UFR SSMT, Université Félix Houphouët-Boigny, 22 BP 582 Abidjan 22, Côte d’Ivoire
² Laboratoire de Physique de l’Atmosphère et de Mécanique des Fluides, UFR SSMT, Université Félix Houphouët-Boigny, 22 BP 582 Abidjan 22, Côte d’Ivoire
³ Laboratoire de Pédologie et de Géologie Appliquée, Université Félix Houphouët Boigny, Abidjan, Côte d'Ivoire
⁴ Laboratoire de Physique de l’Atmosphère et de Mécanique des Fluides, UFR SSMT, Université Félix Houphouët-Boigny, 22 BP 582 Abidjan 22, Côte d’Ivoire
⁵ Laboratoire de Physique de l’Atmosphère et de Mécanique des Fluides, UFR SSMT, Université Félix Houphouët-Boigny, 22 BP 582 Abidjan 22, Côte d’Ivoire
⁶ Laboratoire de Physique de l’Atmosphère et de Mécanique des Fluides, UFR SSMT, Université Félix Houphouët-Boigny, 22 BP 582 Abidjan 22, Côte d’Ivoire
⁷ Laboratoire de Physique de l’Atmosphère et de Mécanique des Fluides, UFR SSMT, Université Félix Houphouët-Boigny, 22 BP 582 Abidjan 22, Côte d’Ivoire

Original language: English

Copyright © 2025 ISSR Journals. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Understanding the necessary relationship between the radar reflectivity factor Z and the rain rate R is still important today and constitutes an interesting challenge for the scientific community. Despite this interest and the advances already obtained in this field, understanding the variability of this Z-R law is not yet trivial. This work therefore consists of studying the implication of rain spectra at low intensities R≤1mm/h in this variability. Thus, from a large historical database of raindrop size distribution (DSD) acquired in tropical Africa, we have shown that rain spectra R≤1mm/h lead to high values of the coefficients A and b of the Z-R power relationship. However, the variability of pre-factor A is pronounced in agreement with those of the NT and D0/NT parameters of the DSD; while the exponent b remains quasi-constant in such rainy samples, independently of their percentage. Establishing the link between the observation parameters D0, NT and D0/NT of the DSD and the pre-factor A of the Z-R relationship made it possible to arrive at close power relationships D0 – A, NT – A and D0/NT – A corresponding respectively to the microphysical modes «D0 constant, NT variable», «D0 variable, NT constant» and «D0 variable, NT variable». The last microphysical condition seems to be more suited to the power relationship A – α where α, is the pre-factor of the power relationship D0/NT – R found in the literature.

Author Keywords: Rain spectra, Low intensity R≤1mm/h, Raindrop Size Distribution (DSD), Tropical Africa, Z – R relationship Variability, observation parameters, microphysical modes.

How to Cite this Article

Bakary Bamba, Augustin Kadjo Koffi, Koné Brahima, Modeste Kacou, Ibrahima Bamba, Eric-Pascal Zahiri, and Abé Delfin Ochou, “Implication of low intensity rain spectra (R≤1mm/h) in the variability of Z-R relationship linked to the microphysical processes of precipitation: Size-controlled, number-controlled and mixed control of drops,” International Journal of Innovation and Applied Studies, vol. 46, no. 3, pp. 563–582, September 2025.

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Implication of low intensity rain spectra (R≤1mm/h) in the variability of Z-R relationship linked to the microphysical processes of precipitation: Size-controlled, number-controlled and mixed control of drops

Abstract

How to Cite this Article