We investigate the relationships among the mass-weighted mean diameter (<InlineEquation ID="IEq3"> <EquationSource Format="TEX">\(\:{{D}}_{{m}}\)</EquationSource> </InlineEquation>), normalized intercept parameter (<InlineEquation ID="IEq4"> <EquationSource Format="TEX">\(\:{{N}}_{{w}}\)</EquationSource> </InlineEquation>), and rainfall rate (R) using five disdrometers and GPM Dual-frequency Precipitation Radar (DPR) observations over the northeastern Indian subcontinent. By extending the conventional <InlineEquation ID="IEq5"> <EquationSource Format="TEX">\(\:{{D}}_{{m}}\)</EquationSource> </InlineEquation>–<InlineEquation ID="IEq6"> <EquationSource Format="TEX">\(\:{{N}}_{{w}}\)</EquationSource> </InlineEquation> framework to include rainfall rate, we directly link rainfall microphysics to rainfall intensity. Rainfall with 1.5 ≤ <InlineEquation ID="IEq7"> <EquationSource Format="TEX">\(\:{{D}}_{{m}}\)</EquationSource> </InlineEquation>< 2.5 mm exhibits a bimodal structure in the <InlineEquation ID="IEq8"> <EquationSource Format="TEX">\(\:{{D}}_{{m}}\)</EquationSource> </InlineEquation>–R–<InlineEquation ID="IEq9"> <EquationSource Format="TEX">\(\:{{N}}_{{w}}\)</EquationSource> </InlineEquation> relationship, consisting of Type A rainfall (<InlineEquation ID="IEq10"> <EquationSource Format="TEX">\(\:{{N}}_{{w}}\)</EquationSource> </InlineEquation> ≥ 36 dB) with high rainfall rates and Type B rainfall (<InlineEquation ID="IEq11"> <EquationSource Format="TEX">\(\:{{N}}_{{w}}\)</EquationSource> </InlineEquation> < 36 dB) with lower rainfall rates. Type A rainfall is more frequent during the monsoon season and over orographic regions. The DPR product shows limited variability in <InlineEquation ID="IEq12"> <EquationSource Format="TEX">\(\:{{N}}_{{w}}\)</EquationSource> </InlineEquation> and rarely reproduces high-<InlineEquation ID="IEq13"> <EquationSource Format="TEX">\(\:{{N}}_{{w}}\)</EquationSource> </InlineEquation> rainfall, leading to systematic underestimation of rainfall intensity. These results highlight the importance of representing <InlineEquation ID="IEq14"> <EquationSource Format="TEX">\(\:{{N}}_{{w}}\)</EquationSource> </InlineEquation> variability for improving satellite-borne precipitation radar retrievals.

Linking Rainfall Microphysics to Intensity Using the \(\:{{D}}_{{m}}\)–\(R\)–\(\:{{N}}_{{w}}\) Relationship Over the Northeastern Indian Subcontinent: Implications for GPM DPR Retrievals

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2026年5月13日

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Fumie Murata,
Toru Terao,
Hiambok J. Syiemlieh,
Laitpharlang Cajee,
Shyam Sundar Kundu,
Sayeed Ahmed Choudhury,
Shah Md Shajib Hossain,
Md. Shameem Hassan Bhuiyan,
Md. Momenul Islam

摘要

We investigate the relationships among the mass-weighted mean diameter ( \(\:{{D}}_{{m}}\) ), normalized intercept parameter ( \(\:{{N}}_{{w}}\) ), and rainfall rate (R) using five disdrometers and GPM Dual-frequency Precipitation Radar (DPR) observations over the northeastern Indian subcontinent. By extending the conventional \(\:{{D}}_{{m}}\) – \(\:{{N}}_{{w}}\) framework to include rainfall rate, we directly link rainfall microphysics to rainfall intensity. Rainfall with 1.5 ≤ \(\:{{D}}_{{m}}\) < 2.5 mm exhibits a bimodal structure in the \(\:{{D}}_{{m}}\) –R– \(\:{{N}}_{{w}}\) relationship, consisting of Type A rainfall ( \(\:{{N}}_{{w}}\) ≥ 36 dB) with high rainfall rates and Type B rainfall ( \(\:{{N}}_{{w}}\) < 36 dB) with lower rainfall rates. Type A rainfall is more frequent during the monsoon season and over orographic regions. The DPR product shows limited variability in \(\:{{N}}_{{w}}\) and rarely reproduces high- \(\:{{N}}_{{w}}\) rainfall, leading to systematic underestimation of rainfall intensity. These results highlight the importance of representing \(\:{{N}}_{{w}}\) variability for improving satellite-borne precipitation radar retrievals.