Table 1 Thermal infrared and hyperspectral reflectance indices evaluated in this study

Thermal Infrared

Canopy Temperature Depression (CTD)

\(CTD={T}_{p}-{T}_{a}\)

[53]

Canopy Stress Index (CSI)

\(CSI =\frac{{T}_{p}-{T}_{a}}{VPD}\)

[54]

Idso’s Crop Water Stress Index (ICWSI)

\(ICWSI=\frac{{T}_{p}-{T}_{min}}{{T}_{max}-{T}_{min}}\)

[55]

Crop Water Stress Index (CWSI)

\(CWSI=\frac{\left({T}_{p}-{T}_{a}\right)-{\left({T}_{p}-{T}_{a}\right)}_{max}}{{\left({T}_{p}-{T}_{a}\right)}_{min}-{\left({T}_{p}-{T}_{a}\right)}_{max}}\)

[50, 56]

Simplified Stomatal Conductance Index (T_dry-T_p)

\({T}_{dry}-{T}_{p}\)

[57]

Temperature Ratio Index (TRI)

\(TRI=\frac{{T}_{p}}{{T}_{a}}\)

This study

T_BS-T_p

\({\mathrm{T}}_{\mathrm{BS}}-{\mathrm{T}}_{\mathrm{p}}\)

This study

Hyperspectral

1^st derivative Simple Ratio index _660/1040 (dSR_660/1040)

\(dS{R}_{660/1040}= {\rho {\prime}}_{660}/{\rho {\prime}}_{1040}\)

[58]

Normalized Difference index _1425/2145 (ND_1425/2145)

\({ND}_{1425/2145}= \frac{{(\rho }_{1425}-{\rho }_{2145})}{{(\rho }_{1425}+{\rho }_{2145})}\)

[59]

Water Band index

(WBI)

\(WBI= {\rho }_{900}/{\rho }_{970}\)

[60]

Simple ratio index _1440/1460 (SR_1440/1460)

\(S{R}_{1440/1460}= {\rho }_{1440}/{\rho }_{1460}\)

[59]

Normalized Difference Water Index (NDWI)

\(NDWI=\frac{{\rho }_{857}-{\rho }_{1241}}{{\rho }_{857}+{\rho }_{1241}}\)

[61]

Relative Moisture Percentage 1483/1430 (RMP_1483/1430)

\({RMP}_{1483/1430}=\frac{{\rho }_{1483}}{{\rho }_{1430}}\)

[62]

Water Content Index (WCI)

\(\mathrm{WCI}=\frac{{(\rho }_{686}-{\rho }_{955})}{{(\rho }_{955}-{\rho }_{548})}\)

[42]

Water Potential index 2 (WPI₂)

\({\mathrm{WPI}}_{2}=\frac{{(\rho }_{665}+{\rho }_{1457})}{{(\rho }_{715}+{\rho }_{1457})}\)

[42]

Ratio index 953/492 (R_953/492)

\({\mathrm{R}}_{953/492}=\frac{{\rho }_{953}}{{\rho }_{492}}\)

[42]

Normalized Difference index 1407/1862 (NDI_1407/1862)

\({\mathrm{NDI}}_{1407/1862}=\frac{{\rho }_{1407}-{\rho }_{1862}}{{\rho }_{1407}+{\rho }_{1862}}\)

[42]