This PACT-1D model release (v1.1) includes all previous model developments of v1.0, which adds chlorine and bromine chemistry as well as polar Cl2 and Br2 emissions from surface snow and snow recycling. This update contains two additional gas-phase reactions involving bromine that were omitted from v1.0. These reactions are Br + BrNO2 and Br + BrNO3.