KMDT/KCXY · Dewpoint + RH

Dewpoint & Humidity

Susquehanna River boundary layer moisture · Both eras · IEM source
Mar MaxDP Early
+3.5°F
Peak river moisture offset
Modern MK MaxDP
p=0.981
Perfectly stable 2001-2025
Early RH Offset
+2-6%
MDT higher all 12 months
Modern RH Offset
+2-4%
Consistent boundary layer
1962-65 Drought
dp→neg
MDT below CXY — anomaly
Max Dewpoint Offset MDT-CXY — Both Eras with 95% CI
Avg RH Offset MDT-CXY — Both Eras
Annual MaxDP Offset — Both Eras (1962-65 drought annotated)
Annual AvgRH Offset — Both Eras

Key Findings

01
MDT is consistently moister than CXY in every month of both eras. The Susquehanna River continuously evaporates into the overlying air mass, keeping MDT's boundary layer more humid than the upland CXY site year-round.
02
March has the peak offset (+3.5°F early) — when river-to-air temperature differential is greatest in late winter. The river stays liquid while air temperatures are near freezing, maximizing evaporation into the cold air mass.
03
Modern MaxDP is perfectly stable (MK p=0.981, Tau=+0.007). This is the most stationary variable in the entire analysis — the Susquehanna moisture signature has not shifted between 2001 and 2025.
04
1962-65 drought collapses the early era offset — MDT max dewpoint actually goes BELOW CXY in 1963-64. This is a meteorological anomaly, not a structural change. Excluding those years the early era is also stable.