Climatology of ShCu bulk entrainment at the SGP observatory

Daniel Kirshbaum, McGill UniversityKatia Lamer, Brookhaven National Lab

ARM/ASR 2020 PI meeting

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Shallow cumuli at the ARM SGP observatory

Method 1: Jensen and Del Genio (2006)

• 2021 individual ShCu cloudsØ Surface-based, cloud tops

< 5 km, depths > 250 mØ Computes fractional

entrainment rate (𝟄) required for parcel LNB to match cloud-top height

• Notable sensitivites: CAPE (+), RH (+), shear (+), cloud-base mass flux (-)ØNo sensitivity to cloud

width (not shown)

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Method 2: Drueke et al (2019; TKE)

• 128 1-h ShCu periodsØ Surface-based, cloud tops

< 5 km, depths > 250 mØ Use scaling of equilibrium

TKE budget to estimate 𝟄

• Strong dependence on RH (+), mb (-) and cloud-layer depth (-)

✏ ⇠ CAPE1/3

m2/3b zcld

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Preliminary conclusions and future work

• Two simple bulk entrainment retrievals give different perspectives on ShCuentrainmentØ Individual clouds vs cloud ensembles

• Robust positive sensitivity to environmental CAPE and RH, negative sensitivity to zcld and mbØAlso, positive sensitivity to vertical wind shear in JDG parcel method

• Future work:ØOther environmental sensitivities?ØDimensional analysis: nondimensional controlling parametersØ ERICA retrieval (Wagner et al 2013)Ø Repeat climatology at ENA site

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